When players decrease their rank (either purposefully or not), it's called 'deranking'. Derank Me allows players in Counter-Strike: Global Offensive to purposefully derank.
There are many reasons for deranking. Some players may want to have a lower-ranked account to play with their friends, and some might want an account they can play on without as much pressure. Or maybe they want to try some crazy strats!
Whatever the reason, our goal is to make it an easy process, with minimal disruption to other players who don't want to derank. We encourage players to gather 5-man lobbies so that non-deranking players don't get stuck on your team by matchmaking.