We will recall first some results about groups of finite rank (Morley Rank or U-rank) and orthogonality, in particular the existence of the socle and the "socle theorem". Then we will explain how this theorem can be used in the context of applications of model theory to algebraic geometry. The first application appeared in Hrushovski's orginal proof of the Mordell-Lang Conjecture (1994). The theorem was used more recently slightly differently in joint work with F. Benoist and A. Pillay.