V2 is the so-called "Take Off safety speed". You will fly this speed in case of an N-1 situation during Take Off. It will provide best single engine climb performance during N-1. (Vx during N-1). As this speed is different for every weight, it is calculated together with V1 and Vr before departure.
V2 shall not be less than 1.2 Vs and 1.1 Vmca.