Traditionally, the term 'gay' refers to people who identify as men who date, sleep with and love only other people who also identify as men. Over the years, however, more and more people on the LGBT+ spectrum came to identify with the term; people of many gender identities and sexual orientations sometimes use it to describe themselves now. The controversy surrounding gayness has mostly to do with the fact that cis gay men are seen and portrayed very differently to many other LGBT+ people - and often wind up as the recipients of a huge amount of the acceptance, understanding, attention and publicity afforded to this group as a whole.
It's very common for someone to fetishise the idea of sleeping with someone who is drastically different in age to themselves. This is usually associated with the Hugh Hefner stereotype, but there's no need for that to be the only way it's perceived; plenty of people prefer a partner with a little more experience, and that goes regardless of gender orientation or sexual identity!
This is sometimes part of a kink, particularly if associated with something like DD/lg or other sexualised role plays, but for many it's simply a matter of to whom they tend to find themselves feeling attracted. A significant age gap can introduce an interesting power dynamic to any BDSM relationship, which many enthusiasts find is a fun added bonus!
Saunas have long had a reputation for being a mainstay of gay sex clubs, but in recent years they've been branching out. Pretty much anyone can enjoy a little playing around in a straight or gay sauna; there's something liberating about the steamy gloom of them, and it's a fantastic spot for exhibitionists and voyeurs alike. Just make sure you've picked the right sauna (your local sex club is one thing; your local swimming pool quite another!) and that you have the consent of all parties involved, including those who are simply bystanders. Make sure you take a few basic safety precautions before having sex in a sauna, too - don't get up to anything too acrobatic, and stay well away from the brazier full of hot coals!