What do those yellow and red cards mean in soccer?

It's a sign that can't be missed, if you have been watching the 2018 FIFA World Cup on FOX 10: referees whipping out yellow and red cards to tell players they have committed a foul or are breaking the rules.

A question that may be on your mind may be: what's up with those cards? Also, how did refs come to use them in the first place?

FOX 10's Steve Krafft reports.