Traditionally, some bathrooms in less-expensive homes or hotel rooms in Europe did not have bathtubs or showers, only toilets and sinks. The bidet was often just a narrow basin on a metal frame. You put a few inches of water in, straddled the bidet, washed your crotch area, and then emptied the water into the toilet. Sponge baths took care of the rest of you.
I've seen bidets in American homes, too. Usually they have hot and cold water faucets, and drains. They can be handy if it's not convenient to take a full bath or shower.
In Japan, you sometimes see very fancy toilet fixtures that can be programmed to wash your bottom with warm water, rinse you off, and even dry you with warm air. Never tried those features, though – the instructions were all in Japanese. At least the flush button was pretty obvious. Their old-fashioned toilets are long, flat basins on the floor. I thought I'd found a better alternative marked "for handicapped", but the only concession to handicapped people was a vertical handhold to help them get up or down.