If the flag was inadvertent, or the official determines that a foul should not have been called, the procedure is to pick up the flag and wave it back and forth, to indicate that the foul is "waved off."
A yellow flag means you have injured a player,foul,just like football.
It usually is called a penalty and is showed by a yellow flag.
To indicate that he has seen a penalty committed by one or more of the players.
most football officials tuck our flag in our waistband. being right handed it is tuck just to the right in front on my knickers
It indicates that a foul has been committed.
The ref can pick up the flag after the play, and usually announces that there was no penalty on the play.
In the game of soccer, a buzzer flag is a flag attached to a buzzer worn by the assistant referee, which causes a receiver to buzz, warning the referee of the flag's use.
If the referee deems it to be delaying the restart of play or unsporting behavior.