First. Do you watch football? Second here are the roles
GK-Goalkeeper
WBL-Wing Back Left (Combine WL and FBL together that type)
FBL-Left Back
CBL-Centre Back, typically left
CBR-Centre Back, typically right
FBR-Right Back
WBL-Wing Back Right (Combine WR and FBR together that type)
DMC-Defensive Midfielder
MC-Central Midfield
AMC-Attacking Central Midfield
AMF-Attacking Left Midfield(Remember all attacking midfields can play any position so it's not wise to buy an AMF no reasons they just can watch football)
AMR-Attacking Right Midfield(Remember all attacking midfields can play any position so it's not wise to buy an AMR no reasons they just can watch football)
DMR-Defensive Midfield Right(Same policy as the attacking AMR,AMF)
DML-Defensice Midfield Left(Same policy as the attacking AMR,AMF)
ML-Left Midfield, can also play as winger
MR-Right Midfield, can also play as winger
WL-Left Winger
WR-Right Winger
CST-Central Striker
RST-Right Striker, can be played as centre e.g David Villa, Neymar JR or a winger
LST-Left Striker, can be played as centre e.g Thierry Henry or a winger
SST-Supporting Striker, normally called CF(centre forward), behind the CST in a 4-4-1-1 formation