They are called "Fouls," and there are over twenty different types of infractions that will result in a penalty, usually in the form of yards lost or gained.
See the attached link for a complete list.
Yellow flag
In a game of flag football, any receiver is eligible to be thrown to after the ball is hiked. Regular football games have more strict rules, but in flag football, you can throw to anyone.
A yellow flag means you have injured a player,foul,just like football.
In the NFL, "flag" is usually used as slang for the yellow penalty markers which are thrown by the umpires, referees and side judges.
The head coach is the person who carries the challenge flag and makes the final decision of whether to throw it or not. A challenge is initiated as soon as an official on the football field recognizes that the challenge flag has been thrown.
Flag football or touch football
yellow
flag football flag football
yellow flag by itself means healthy yellow flag flow with another means quarantine
There's no yellow on the Chinese flag
There is no tackle in flag football
the best flag of football is liverpool