Recoil is the force the gun creates when being shot.
As you know, when you fire a weapon, it jumps backward, that's recoil.
Recoil is a bad thing, but can be good.
It depends on the player.
Most prefer less recoil.
So here's a little piece of advice.
Less recoil can be used for knowing where your bullets go, but also depends on bullet spread.
More recoil can be used for aiming at the chest, and allowing the recoil to make the chrosshair jump upward. Thus giving you a headshot.
Though, that isn't necessary, since headshots are a one shot kill.
So lower the recoil, the better.