ReShade used to be called SweetFX. It's a bunch of post-processing shaders, used for improving the look of a game. You can do stuff like depth of field, color correction, sharpening, blurring, vignette, bloom, etc. Each effect is done through a separate shader, and you can install various shaders. It does take extra resources to run. It works by hooking into DirectX through a DLL that you install into the game directory.
Unfortunately, it doesn't currently support VR (afaik). I believe people using ReShade for VaM right now are using it only in desktop mode.
If you want post-processing in VR, then there's MacGruber's PostMagic. It uses shaders that are already built into Unity. I don't use it because most of the effects are not really suitable for first-person VR (when looking from a "realism" perspective).
Edit: Aaaand someone just posted today that it's possible to use ReShade in VR now:
i just tried this in vr and didnt notice any difference, anyone else have any different experience? on the desktop whoa.. huge diff, but didnt really see anything in vr
I have reshade's dpx and adaptivetonemapper looking really nice on desktop mode but the vr mod just doesn't seem to work for vam. :sadface: Anyone know of any other ways to get reshade working?