The Foregrip is an underbarrel attachment in Crysis 3.
Foregrip give more stability, both while aiming and shooting. This means the recoil will be reduced and giving more stable sustained fire. The disadvantages are slower draw time while switching from another weapon and loss of the secondary fire mode. Attaching Foregrip with Muzzle Brake gives maximum stability.
It very useful for high-recoil rifles such as Grendel for sustained fire (burst fire mode).