Kotatsu is a square or rectangular table with built in warmer inside, and a futon around it to keep your legs warm when sitting down. It is mostly seen in Japan but it is said that they have similar ones in Iran called, Korsi.
But this kotatsu, may sound very simple, and may sound like a table with a heater but since in Japan where not many houses heated automatically, it is used a lot and is favored by many during the winter time.
A typical picture of a family in winter is where everybody is joined in this kotatsu and eating the nectarines (since it is a winter fruit), watching TV or talking. Kotastu plays a very symbolic part in Japanese winter. And today they have many kind of kotatsu from small to big, and in many colors too.
The trend is to change the futon. Today they come in many variety and many colors so by changing these futons, the mood of your room changes instantly. And this kotatsu used to be a family furniture, where many families own it but not students or people who lives alone, since it is a big furniture. But today, they are making smaller sized kotatsu which would fit in their apartments and in a cheaper price too.
So if you want to enjoy the Japanese winter with the one and only kotastu custom here in Japan, what are you waiting for go find one and enjoy customizing the futons! :)