Defender (association football)
Centre-backs are usually positioned in pairs, with one full-back on either side to their left and right, but can be played in threes with or without full-backs.
Defenders fall into four main categories: 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 specialised for certain formations dependent on the manager's style of play and tactics. Centre-backs are usually tall and positioned for their ability to win duels in the air.