it stands for Field of View... it basically zooms your viewing angle out so you can see more things on screen, and also it helps a lot in terms of motion sickness. A lot of FPS games are starting to implement them now because people ask for it for the obvious reasons, I personally can't play any shooters below 90 fov, if the game itself doesn't have it, I will go on google and try to find a hack file that enables a custom FOV....
I have the PC version of the Dying Light and it's in my GAME setting if I remember correctly, but I think they don't allow such options on consoles because of the strict specific optimizations consoles adhere to, and adding adjustable FOV could potentially fck it all up by messing up the framerate since it's showing more things on screen.
here's a screen shot of how a 60 FOV looks compared to a 120 FOV works from Battlefield 4 I think... don't let the image fool you though, it looks like you went from a super low resolution to super HD... it's sort of like that, but there's also a stretchy zoom effect the higher up you go.... so a maxed out FOV looks like shit in most cases, I personally use about 90-100 myself, most games max it out at about 120
