Gay S&M is part of the BDSM umbrella. And stands for sadism and masochism.
This means that it’s made up of two types of individuals.
Firstly, you have the sadist. The guy who inflicts the pain.
Secondly, you gave the masochist. The guy who loves nothing more than receiving that pain.
Sometimes partners will switch. They’ll take turns being active or passive.
And then of course you have the pain itself. This is frequently physical. But it can also be emotional or psychological.
However, crucially, all acts involved in Gay S&M must be consensual. It’s never the same as sexual violence.