Where men can go to have anonymous sex along with a sauna.
Depending on the establishment itself, it is generally where you can rent a small cubicle, some towels, and get laid. Random sex is common, and include glory holes & other amenities for getting off without the hassle of buying drinks, or hiring a hustler. You can also get steam, or a massage, if available.
A lot depends on the establishment itself, as well as local laws. A take off on the traditional 'steam baths' which was more of a club for men, to get a steam, associate with others.
The basic concept was for men to meet in private, to engage in sexual practices without any strings or attachments. To satisfy their need for certain sexual acts, with multiple anonymous partners.
Believe it or not, gay baths date back to the 15th Century. There are records in Florence Italy of decrees against bath house operators to insure no queer sex happened in their establishments.
There are many historical references to raids on 'gay bath houses' from Paris in 1876 to New York in 1903. Guess the world has always had homosexuals, and tried to punish them.
One of the most famous American one, was established in 1888 in New York, called the Everhard. (Think about it) In fact it lasted until 1986.
There are others, such as the one in London (Jermyn Street Turkish Baths), that opened in 1857 and lasted until the 1970's. Even then we had a fashion sense, as Jermyn Street is well known for it's fine shirt shops. No wonder a bath was opened there, where old men could take steam, examine hot young boys before having 'tea' with them.
California was the first to actually make gay bath houses legal, by passage of a 'consenting sex bill' in 1976. However that quickly pales in the 1980's due to the health concerns associated with AIDS.
Many gay baths lost their popularity during the AIDS epidemics, and many regulatory bodies clamped down on them as well, for fear of the disease spreading to the non gay population.
One usually rents a towel, locker or small cubicle. There might other charges for certain features, such as a video room, or drinks or such, depending solely on the licenses and location.
Usually one undresses in a common locker room, then heads to a boarded off cubicle, where they can expect to have visitors. The sex is random, anonymous.
There can also be specialized rooms such as 'glory holes' which is even more anonymous.
Sex is not confined to cubicles as it can be within open public areas of the establishment, such as the Locker room or in the steam rooms or sauna or whatever other amenity is provided.
A primary use of these bath houses, is for safety. However, as being gay becomes more accepted, in some locations, it is no longer about protection. The idea being, that entry concealed one's true purpose or sexual orientation. It was a way for men to have sex with other men, and not be outed.
Many popular icons are noted for their frequent attendance at some of these establishments as well. Such as Truman Capote, and Bette Midler. In fact some say she got her start at the Continental Baths of New York, where she created her persona 'The Divine Miss M'. Barry Manilow accompanied her on piano, in a towel.
A bath house, in a non sexual in nature, but simply where men can gather in private, usually in a large steam room, or collective hot tub, to relax, unwind, or socialize.