To see a good use of fsr try dota 2 game its free on steam or riftbreaker demo on steam, they have fsr and easier to to see the benefits of fsr, just to see what quality is like and the fps boost is like, fsr in x4 might not be as impactful as other games.
But yes all info on how it works, with examples of quality and what setting does what, this is the page to read properly.
https://gpuopen.com/fidelityfx-superresolution/
Why use it, well ssr are costly and vol fog is costly render items etc, now you should be able to max those effects out ingame and use fsr and not see a drop in performance or get more fps depending on if the game is gpu bound for you, fsr also sharpens up details so somethings could look bit nicer with it on using ultra mode at 1440p or 4k monitors.
Tried it using super res so i can use higher res than 1440p on my monitor, 4k was a bit much maxed and 2x msaa but 1800p seems ok.
No fsr - 45 i think it was fps.
https://steamuserimages-a.akamaihd.net/ ... rbox=false
Fsr on ultra: 65fps
https://steamuserimages-a.akamaihd.net/ ... rbox=false
Settings used:
https://steamuserimages-a.akamaihd.net/ ... rbox=false
Input lag seems better, less shimmering on railings i think, mouse moves quicker/smoother maybe.