mmm...Futon(布団：ふとん) means usually about a bed. Futon can also distinguish between shiki-buton(敷き布団：しきぶとん) and kake-buton（掛け布団:かけぶとん）.
Kake-buton means usually about a quilt or bed colothes, which put over someone. Shiki-buton is a kind of mattress under the body. In Japanese style of bed(such as http://ja.wikipedia.org/wiki/%E7%94%BB%E5%83%8F:Stage_of_Japanese_pillow_fight.jpg), a shiki-buton is put on the tatami (or sometimes another mattress put between tatami and shiki-buton in order to make more comftable). Japanese Onsen Ryokan (Japanese style of Hotel) uses such style.
