So, you work as an extra? an extra what? The film business is full of strange-sounding jobs. If you read credits (the writing at the end of a film), you will notice jobs like these :
Extra an actor with a small background part.
Best boy Assistant lighting person.
Grip The person who lifts the heaviest camera equipment.
Dolly grip A special grip who pusher the dolly' (a camera platform that moves on tracks).
Clapper The person who his the slate before every shot. (The slate is board with the scene number written on it.)
Boom operator The person who holds the microphone the end of a pole. The pole is called a boom.