Sevens rugby is a faster, shorter version of the 15-a-side game, with - obviously - seven players on each team.
It's played on a full-size pitch so players need a lot of puff, but each half is only seven minutes long so players don't have to keep running for very long.
The rules are the same as the main game, with scrums of three players.
It can look a little strange at times, with the teams spread across the pitch slowly passing the ball to find a gap.
But when a gap appears the match flies into life, and sprinted tries from one end of the pitch to the other are not unusual.
Sevens rugby also takes place at international level with the IRB sevens world series.
The series takes place in eight locations around the world, on eight different weekends during the season.
Countries win points depending on how well they do in each tournament, and the team with the most points at the end of the series is the champion.