What does 'first goal scorer' mean during a football game?

The first one to score - this bet refers to the first goal of the match. Bets on players who do not participate in the competition or enter the field after the first goal is declared void.
 
If the match ends in 0-0, all valid bets are considered lost. For all other goal-related bets, the named player(s) must be present at kick-off for the bet to be valid. Own goals never count as a goal scored by a player.