Why would someone get sin binned?

Why would someone get sin binned?

Mike Schmid (Director of Rugby, Esher RFC) gives expert video advice on: What is a foul or penalty?; What is a penalty goal?; Why would someone get sin binned? and more...

Somebody would get sin binned because the referee has deemed that they are either a repeat offender or their infraction is serious enough to warrant them receiving a yellow card, which means they get to spend 10 minutes off the field.