A sauna bed is an infrared enclosure you lie in rather than sit in: usually a clamshell, a dome over a table, or a padded bed with emitters above and below. They are common in spas and increasingly sold for homes, and they are a genuinely different product from a cabin rather than a horizontal version of one.
The formats
A clamshell closes over your body with your head out. A dome is a half cylinder that rolls over a massage table. A bed has emitters in the surface you lie on and sometimes a canopy. All three are infrared, all three leave your head in room air, and none of them heats an enclosure the way a cabin does.
What lying down changes
Contact with a warm surface does much of the work, so the sensation is closer to a heated mat with radiant panels above than to sitting in hot air. People who dislike sitting upright in heat often much prefer it. People who want the enveloping feeling of a sauna usually do not, and that split is worth testing before buying.
Where it fits at home
It needs floor space when open and stores against a wall or under a bed when closed, which suits an apartment better than a cabin does. Most run on an ordinary outlet. It is also the only format that works if standing or sitting for twenty minutes is difficult, which is a real reason people choose one.
What to check
Emitter coverage above and below rather than only underneath, a maximum temperature and a timer, a surface you can actually clean, and what the maker states about EMF as a measurement rather than an adjective. And read the warranty for the emitters specifically, because that is what fails on any infrared product.
Questions people ask about sauna bed
Is a sauna bed the same as a sauna?
No. It is an infrared enclosure you lie in with your head out. There is no heated air and no enclosure around you in the way a cabin has.
Does it work as well as a cabin?
It makes you sweat comparably and feels quite different. Whether that is better is a preference worth testing rather than assuming.
Does it need special wiring?
Most run on an ordinary outlet. Check the stated amperage as you would with any infrared product.