What causes a red card in football?

What causes a red card in football? A player is sent off and shown the red card if he commits any of the following offences: S1 is guilty of serious foul play. S2 is guilty of violent conduct. S3 spits at an opponent or any other person.

A player is sent off and shown the red card if he commits any of the following offences: S1 is guilty of serious foul play. S2 is guilty of violent conduct. S3 spits at an opponent or any other person.