Princess Leia marries Han Solo.
As every Star Wars fan knows, about four years after the Battle of Yavin depicted in A New Hope, the Rebel Alliance destroyed the second Death Star. The Prophecy of the Chosen One spoken about in Episode I is seemingly fulfilled with the destruction of the Sith. Former Jedi Knight Anakin Skywalker, with the help of his son, kills the Emperor, thereby destroying both Darth Sidious and his own alter ego, Darth Vader. As detailed in the new canon novels Aftermath: Empire's End and Aftermath: Life Debt, Rebel leaders Leia Organa and General Han Solo are married on the forest moon of Endor.
Luke recovers an artifact hidden by the Emperor.
Luke Skywalker tells R2-D2, "If the Empire is here, then what I sensed is true. There must be something special about this place." The new age Jedi Knight and Rebel Commander came to Pillio in search of an Observatory where the Emperor hid various artifacts behind an entrance only accessible to a Force wielder. Luke leaves there with an old compass, as depicted in the 2017 video game Battlefront II.
Battlefront II and the four-issue Shattered Empire comic series detail Operation: Cinder, a contingency plan crafted by the Emperor himself and posthumously ordered via hologram. Imperial admirals are tasked with devastating environmental attacks on a handful of worlds, including Naboo. With the assistance of two key Imperial defectors, Princess Leia's forces successfully defeat Operation: Cinder.
The New Republic is born.
In the novel Aftermath, we see the dissolution of the Rebel Alliance and the formation of the New Republic, built on the democratic principles of the Old Republic, with the planet Chandrila chosen as the seat of the newly restored Galactic Senate. After her election as Chancellor, former Rebel Alliance leader Mon Mothma unveils plans to reduce the size of the military and to give up the emergency powers and authority given to Palpatine in Star Wars Episode II: Attack of the Clones.
The connection between Luke Skywalker and Poe Dameron.
In his continuing search for artifacts housed in secret Imperial facilities, Luke located two fragments of the Great Tree that was once at the heart of the Jedi Temple on Coruscant. As detailed in Shattered Empire, Luke kept one fragment and entrusted the other to Shara Bey, who plants it on Yavin IV after retiring from the New Republic military. Bey's husband is Kes Dameron. They have a young son, Poe.
Han and Chewie liberate the Wookie home planet.
In Aftermath: Life Debt, Han Solo and Chewbacca organize a ragtag team of bounty hunters and smugglers who help the New Republic liberate Chewie's home planet. With Kashyyyk free, Star Wars most famous Wookie retired. His retirement didn't stick, but the retirement of Chewbacca actor Peter Mayhew was made official in 2017. The man who was inside the suit since the 1977 original passed the torch to the Finnish actor who shared the role in The Force Awakens, via a touching letter.
The final defeat of the Empire.
The Battlefront video games and the novels Lost Stars and Aftermath: Empire's End detail the final defeat of the Empire, when the Imperial Remnant was beaten on the planet Jakku, leaving behind the Starship Graveyard seen in The Force Awakens. Eventually, the two sides sign the Galactic Concordance, in which the Empire agrees to dissolve its larger government, cease military operations, and cede several planets, including Coruscant, to the New Republic. Some of the details of this information are found in the book Star Wars: The Force Awakens Visual History.
The First Order forms in secret.
Different factions of course refused to surrender, continuing a small bit of fighting on Jakku before jettisoning off into the Unknown Regions to regroup. Admiral Rae Sloane is among those who secretly rebuild the Empire, which becomes The First Order. In the novel Bloodline, renegade Galactic Senate members and various criminals secretly help the First Order gain capital to rebuild the Imperial Navy.
Leia sends Ben Solo to train as a Jedi knight.
Leia entrusts her brother Luke to train her son, Ben Solo, as a Jedi Knight. Her hope is that the Force sensitive young Solo will be protected from falling to the Dark Side.
The Resistance begins.
Leia is forced to resign from the Galactic Senate after she is exposed as the daughter of Darth Vader, even as Centrist Senators plot to secede and join the First Order. Leia and Admiral Ackbar form the Resistance. They are later joined by New Republic Commander Poe Dameron and Rapier Squadron, his team of X-Wing pilots. This takes us right up to the events of The Force Awakens and Star Wars: The Last Jedi.