Used in many sports the yellow card it's most likely to indicate caution for bad behaviour. In football it is shown by the ref to indicate that a player has been cautioned. Then the ref records the players details in a small notebook. This action is most known as "booking."
Some reasons for booking are:
- Unsporting behaviour
- Dissent by word or action
- Persistently infringing the laws of the game
- Delaying the restart of play
- Failing to respect the required distance of a corner kick or free kick
In some tournaments, the accumulation of a certain number of yellow cards over several matches results in disqualification of the offending player for a certain number of subsequent matches, the exact number of cards and matches varying by jurisdiction.