Short for Central Midfielder. A central midfielder, often known as a centre midfielder (CM), is a midfielder whose job is to play equally in attack and defence while dominating play in the middle of the pitch.
Short for Central Defensive Midfielder. A central defensive midfielder is a centre midfielder who is primarily responsible for defending the goal of their side. CDM players may assist their team's defenders in front of the defence or man mark individual opposition attackers.
Short for A Central Attacking Midfielder. A central attacking midfielder is a central midfielder who plays predominantly on the offensive side of the field, usually in an advanced midfield position between central midfield and the team's forwards.
Short for Right Midfielder. A right midfielder is a wide midfielder who plays a role that is balanced between attack and defence, similar to that of a central midfielder, but on the right side of the pitch and closer to the touchlines.