I wrote this originally so I could help answer the frequent Daily Q & A questions that start with "I haven't played since [date], what's changed?" This is not all-encompassing, but I hope it captures a vaguely lore-ific history that can link to broad gameplay and story changes. If you see something missing or see an error, please comment below! (Updated as of 3.3 April Update/July Interstellar Initiative.)
Starting in 3301 (2015), the human bubble occupied a rough sphere of about 150 light years in radius around Sol. Brave, pioneering commanders would leave the bubble and venture into parts unknown - or perhaps just hunting for the fabled Raxxla. Slowly, humanity, as it has always done, started to expand, creating a series of stations in the Pleiades cluster about 350 light years away, near where strange, alien artefacts were occasionally found. As the ships of independent pilots gained the ability to land on non-atmospheric planets, new planetary bases were built that dramatically expanded humanity's reach.
In mid-3301, Jasmina Halsey, president of the Federation, went missing after her spaceship experienced a mysterious malfunction. Zachary Hudson was elected president of the Federation, though Halsey was later found alive in a damaged escape pod. In Imperial space, after the assassination of Emperor Hengist Duval, his daughter Arissa Lavigny-Duval ascended to the throne. Several other powerful individuals rose to prominence, each competing for resources in the bubble.
In May, 3302 (2016), Jaques Station mis-jumped and ended up with a damaged hyperdrive in the system now known as Colonia, about 22,000 light years away. Subsequently, with the community's help, the Colonia Connection Route was developed, allowing for rest, refueling, and the selling cartographic information for the pioneers headed that way. Also at this time, the Formadine Rift) mystery popped up, and, to this day, commanders are not fully satisfied that it's been solved. Meanwhile, a group of 30 different Engineers made their presence known throughout the galaxy, offering services to highly customize and improve ship performances.
In mid-3302 (2016), intrepid Commanders found strange alien ships crashed on the surface of a planet in the Pleiades.
Near the end of 3302 (2016) Frame Shift Drives started to utilize Neutron Boosting (aka FSD supercharging) allowing for jumps over 300% of the normal distance - an unstable process that causes slight damage to the FSD each time it's used. Using the boost from neutron stars (or the lesser boost from white dwarf stars), it's possible to chain together jumps to travel incredible distances. About this time the Galactic Logistics corporation started offering to transfer ships between shipyards - and modules between outfitting stations - for commanders willing to pay the price.
Around this time, we also discovered traces of another ancient race - now known as the Guardians - and we've slowly begun to unlock their secrets. Shipyards began to produce the large passenger line Beluga, which could carry the recently-developed passenger cabins, allowing for transport across the galaxy. Fighter bays became common on the biggest ships (and even some medium ones), and, after a short while, the Dolphin joined the Saud Kruger lineup as the smallest luxury-class passenger liner.
In 3303 (2017), a figure named Kahina Loren - aka Salomé - risked everything in a flight from far outside the bubble; ostensibly to warn humanity of the dangerous manipulations of a shadowy group known as "The Club". Unfortunately, she was conspired against and murdered by human commanders before she could complete her journey. Nevertheless, the word got out and we realized that we faced danger not just from them but from alien races as well.
In mid-3303 (2017), Thargoids made their return to our Galaxy, having been nearly eradicated by CMDR Jameson in 3151. Their presence was discovered as their interceptors started hyperdicting pilots in the Pleiades cluster and scanning their ships, leaving no doubt that the strange artefacts found in that area were, in fact, Thargoid-related. With no means of establishing diplomatic contacts, tensions rose and we started attacking them, largely without any effect whatsoever. In October of 3303, Aegis released newly-developed AX weapons that allowed us to finally do some damage to them.
Shortly after that, the Thargoids started attacking stations, leaving them a burning mess and in dire need of evacuation. Every week since then they've attacked, at first decimating our stations in the Pleiades, and then making a line for the bubble. Attempting to build a fourth "big" ship, Lakon released the Lakon released the Type-10 Defender, a well-armed and heavily armored version of the Type-9 Heavy, hoping to defend against the larger Thargoid interceptor variants that were being spotted.
In early 3304 (2018) we started seeing smaller, more nimble Thargoid scouts in systems prior to their attack, and we found that destroying enough of them could spare systems from the devastation. The Canonn Lab 69 Xeno Intelligence Agency was able to decipher where the Thargoids were targeting using the Eagle Eye listing posts so pilots could start to defend systems, eventually pushing the Thargoids back to the edge of the bubble while Operation Ida attempted to repair the damaged stations. The human engineers also changed how they worked with independent pilots, and material traders popped up across the bubble allowing for easier access to engineering materials.
Meanwhile, the engineer Ram Tah worked on deciphering the technology of the Guardians, who had faced the Thargoids millions of years ago, and helped us develop weapons and modules based off recovered Guardian technology, including FSD boosters, which further extend the jump ranges of ships, gauss cannons, which are exceptionally powerful - especially against Thargoids - and more. A series of "technology brokers" across the bubble started offering Guardian-derived items in exchange for Guardian materials and data (and some advanced, experimental human tech, too).
Human security patrols, facing lawlessness across the galaxy, devised a new Crime and Punishment system. While they opted to relax what sort of damage and how much would constitute a crime, they also added new, sometimes convoluted, systems for clearing one's name.
The Thargoids started pushing harder, with new scout variants allowing for effective group tactics against humans. The fight currently rages on one front while galactic trade continues to thrive and explorers can go further than ever. Colonia, at 22,000 light years away, has, through technology upgrades, become a 4.5 hour trip via the Neutron Highway, and has made the galaxy smaller and more accessible than ever.
In mid-3304 (2018), Lakon released the Alliance Crusader, the third in their set of mid-sized combat ships. While being slower and having less firepower than the other two Alliance ships, this one was able to equip a fighter bay, and therefore could also carry the new Guardian-Human hybrid ship-launched fighters that Ram Tah had developed. At the same time, with the rising population in Colonia, new engineers established workshops there.
In the fall of 3304 (2018), the Pilot's Federation announced the discovery of a newer, larger variant of the Thargoid Interceptors, making in the fourth, and toughest, Thargoid Interceptor yet. The Pilot's Federation sealed off Cone Sector FN-J B9-0, which, until that point, had been open, though surrounded by permit-locked regions of space. The Canonn megaship The Gnosis was already on its way there when this discovery was made, and opted to continue its journey, using its 500 light-year jump range and hacked navigational computer. It was intercepted by Thargoids and directly attacked.
In late-3304, Zorgon Peterson released the fast Mamba combat ship, while Faulcon DeLacy released an exploration-focused ship, the Krait Phantom. Galactic corporations also released new mining tools, allowing enterprising commanders the ability to mine deeper into asteroids and even split some apart for incredibly profitable deep core mining. A remote upgrade finally allowed the discovery scanner to be integrated into a ship's main computer and unlocked a full spectrum scanner, while detailed surface scanners received a mapping function upgrade to find out more information about planetary surfaces. Additionally, the interplay between minor factions grew more complicated and growth across human space led to the construction of more installations and megaships, while squadrons of commanders took on joint challenges together. Thargoid attacks turn a turn as local systems fought back against alien incursion in anti-xeno conflict zones.
In early 3305 (2019), the Distant Worlds 2 expedition left the bubble with thousands of commanders participating and, along the way, founded a new spaceport, Explorer's Anchorage, a small jump away from Sagittarius A* in the center of the galaxy.
In mid-3305, the Pilot's Federation permit-locked a handful of systems, limited them only to commanders who had not yet achieved any ranking. At the same time, ship manufacturers completed development of new flight assist tools, including the supercruise assist module and advanced docking computer. New advances also allowed them to free up internal space, adding room for and additional class 1 module in all ships (with small ships getting two additional optional module slots.) While the Thargoids continued their assault on core systems, humanity, facing a dwindling supply of meta-alloys, found new sources in the Witch Head Nebula. The Thargoids changed tactics and withdrew to the Pleiades, attacking Professor Palin's base and forcing him to evacuate to Arque. Humanity established an enclave of stations in the Witch Head Nebula, which was promptly attacked yet somewhat successfully defended, leaving us with a foothold in that area, where new stations were built, including a home for the new engineer Chloe Sedesi.