"Extra Time", or ET, refers to extra periods of play that break ties after two full halves, plus "stoppage time" is complete.   


North Americans would call this "overtime".

The minutes the referee adds on at the end of each half are properly called "stoppage time". 


Some who have wagered or played soccer for many years may refer to it as "injury time".

These definitions are accepted worldwide by both players and bettors of soccer.