A player is "capped" for each international match played. Some "friendly" games also count. A player who has played in 50 international matches has fifty caps.
The origin
It stems from the old days when the players were issued commemorative "caps" for the game; the term has simply continued, although the actual caps are no longer provided to the players.
See related link, "International cap", for a photo of a cap.
Pat Jennings with 119 caps
Well in the begining there was no helmet then it evolved into leather caps then into plastc caps then facemasks then chinstraps
Elikobi
Casillas I think
Calum MacDonald has a total of 122
50
caps rzmvm
Claudio Suarez i think is 144.
Fudge caps mean you are eating chocolate that is high in sugar. A high sugary snack.
For England it is Peter Shilton with 126 caps.
The players switch in and out after a play. There is no official required to bring a player in or out.
Priceless. I have them that I collected and I would not part with them.