Eversion is the opposing movement to Inversion. The bottom of the foot moves toward the lateral side of the body. This movement is very limited in its range; the foot can seldom move very far in the lateral direction. Therefore, eversion is often simply the movement that occurs following a prior Inversion so that the foot returns to is normal position.
Eversion is an important movement when you are moving across uneven terrain or if you are standing in Ippon Dachi. Subtle inversion and eversion movements enable you to maintain balance in these situations.