Elite Dangerous Odyssey added the ability to walk around planets and complete missions on foot to Frontier's vast space sim. It also added lots of bugs, performance issues, and features which felt incomplete. Frontier have been patching the game since, and the latest update is a big one.
The biggest change is that shared missions have been added. This means that any of the missions added in Odyssey can be shared with teammates, letting you tackle them together and share the rewards.
After that, there are simply hundreds of fixes, balance changes and visual tweaks. Terrain will look better at ports, neutron stars aren't so bright, AI crime scanning has been "softened", certain loot drops are more generous, and what seems like a hundred other things have been fixed according to the full patch notes.
It's worth noting that, although it was broken, bugs weren't the only problem with Odyssey. Brendan explained in his Elite Dangerous Odyssey review that its weapons felt bad to shoot, its space ports seemed sparse and repetitive to walk around, and its exobiology activities were deathly boring.
He did end on a note of hope, wondering whether Frontier would fix the issues and feeling certain that it would be a good entry point for new players to the space sim when that had happened. This patch sounds as if it's a step closer to that point.