What are inverse kinematics?

Inverse kinematics are a quality that gives a model a better way of interacting with other models connected to it, in that the motion of one model affects that of others linked to it. Thus, if the hand moves, the arm moves, which moves the body (instead of always being the other way around). This allows such things as realistic recoil effect (a player will be kicked back by the recoil), and other things like the realistic suspension effects seen on the jeep.