Here'some basic information if you're just getting started: Most mods for Icarus are QoL (quality of life) tweaks, or improvements of existing game mechanics. These usually speed things up, make things easier, or generally facilitate less grinding (or make the grind more fun).

But there are also a few totally new innovations - brand new technologies that can fundamentally alter/improve gameplay (such as the Teleporter and Elevator mods by Jimk72, and Reaper's Mini-map). There’s even a mod by TheOrangeFloof that allows players to gain talents and keep increasing past level 50 - an essential improvement!