Futon  a kind of mattress that is part of  a Japanese bed.
Sold In Japan in Department Stores and special shops calle futon-ya

They are fairly thin with only a thickness of 2 inches. and an outer layer stuffed with cotton or a synthetic stuffing material.
They are usually sold in a complete set with the matterss,comforter,blankets and a pillow which is generally stuffed with buckwheat or beans.They must be aired in sunlight regularly.
Many Japanese people beat their Futons with a sort of bamboo carpet beater.
It is meant to be used on a Tatami Mat and folded away when not in use.
Futons are what you are usually offered in Japanese Inns.
 

Western Futons Only generally based on the Japanese Original.
They are usually supplied with a frame which can double as a bed,couch or chair.
The Frame usually folds in the middle and then the futon converts into a couch.
When flattened it turns into a bed.
Western Futons are usually supplied with a foam filling in several layers and these are thicker and bigger than Japanese Futons and look more like a western mattress.
They are cheaper but look much more like a Western Bed