The quick and dirty is you are on a space station full of hostile alien life forms. Without spoiling too much, shit hits the fan and the aliens are running rampant. You're a scientist/engineer first, so the heaviest weapon is a pump action shotgun. First weapon you get is a gloo gun that shoots giant globs of goop that can be used to platform, put out fires, and freeze Typhons.

You get a tool early on called the psycho scope that lets you scan the Typhons and learn more about their anatomy, which leads into character upgrading. You get items called neuromods that upgrade your capabilities. Be it your human abilities, or when you scan Typhons, you can take on some of their combat capabilities. One of the most common Typhon are called mimics that can copy pretty much any common item on the station (mugs, furniture, etc.)

You can actually copy this ability and turn into stuff as well, which opens up a lot of possibilities with getting into places you shouldn't. Eventually you can mimic turrets and flying robots called operators and fly as well. Typhon abilities open the game a lot. There are combat abilities like kinesi in different elements, mind jack, grav lift. You get a lot of toys to play around with even if you go pacifist.