A steam shower is an ordinary shower enclosure that has been sealed and given a steam generator, so the same space serves as a shower and, separately, as a steam room. It is the most common way steam gets into an American house, because it uses a room that already has water, drainage and tile.
How it works
A generator sitting outside the wet area boils water and pipes vapour to a head low in the enclosure. A control panel inside sets temperature and run time. Because steam rises and condenses on every surface, the enclosure has to be sealed top to bottom, including the door, or the steam simply leaves and your bathroom mirror takes the benefit.
Against a steam room
The difference is dedication rather than technology. A steam room is built only for steam, often larger, with benches and a sloped ceiling designed for it. A steam shower is dual purpose and therefore compromised: smaller, usually with a fold down seat, and with a ceiling that may not shed condensate as well as a purpose built room does.
Against a sauna
A sauna is dry heat in a wooden cabin and needs no plumbing at all. A steam shower is wet heat in a sealed tiled box and needs water, drainage and waterproofing. If you are not already renovating a bathroom, the sauna is much less building work for a comparable experience, which is the honest comparison most buyers should make first.
What your bathroom needs
A fully waterproofed enclosure rather than tile over board, a door sealed at the top, a ceiling with a slight fall, a drain, and a dedicated electrical circuit for the generator sized to the enclosure volume. Retrofitting all of that into a finished bathroom is the reason steam showers are usually specified during a renovation rather than after one.
Questions people ask about what is a steam shower
Can you use a steam shower as a normal shower?
Yes, that is the point of one. The steam function is separate and the space works as an ordinary shower the rest of the time.
Is it the same as a steam room?
No. A steam room is purpose built for steam, usually larger and with a ceiling designed to shed condensate. A steam shower is a dual purpose compromise.
Does it need special glass?
It needs a sealed enclosure including the top of the door. Standard shower glass that stops short of the ceiling will not hold steam.