Defender (association football)
Centre backs are usually in pairs, with two full-backs to their left and right, but can come in threes with no full backs.
There are four types of defenders: centre-back, sweeper, full-back, and wing-back. The centre-back and full-back positions are essential in most modern formations. The sweeper and wing-back roles are more specialized for certain formations depending on the managers choice of play and adaptation.