The British and Irish Lions are a touring team selected from all four home unions, England, Ireland, Scotland and Wales.
A Lions tour takes place every four years and they play against South Africa, Australia and New Zealand in turn, so each country hosts the Lions once every 12 years.
It's a honour to be selected for the Lions and the best-of-three series are often very exciting.
Traditionally the touring squad is big enough to support two teams, the Test side and the midweek team, although players often move between the two.
The Test side plays the Tests against the national sides each weekend, while the midweek side tends to play against smaller teams in between.