There are two types of entrance in a sento, the bandai and the furonto. Both are where you have to pay the fees to enter.
Bandai (番台): old style desk entrance in the middle of women and men’s baths.
Furonto (フロント): Before entering the bath, this is a modern front desk version
Datsuiba (脱衣場): the dressing room, you can find the lockers and change your clothes. Most of the time you have also the toilet, hair dryer, and sometimes garden, television, massage chair, books and various services according to each sento.
Yokutshitu (浴室): the bathroom. When you enter the bath you will find a basin and a small stool. In the bathing area there is first the shower space, and the bathtubs. At least one is a hot bath and depending on the place you can find several kinds such as: cold bath, massage bath, warm massage bath, aromatic bath, electric bath, sauna (utilization of the sauna may require an additional fee, most of the time between 200-400 yen) and sometimes you can even an find outdoor bath (rotenburo).
Penki (ペンキ): the wall painting. In a lot of sento you can admire a penki, the most common is the Fuji-san painting, but also many other Japanese landscapes and landmarks are depicted.
There are three painters of penki in Tokyo : Morio Nakajima san (中島 盛夫)and Kiyoto Maruyama san (丸山 清人) and Mizuki Tanaka (田中みずき). (article : http://www.tokyo-sento.com/sento-art/ )ometimes it is a not painting but a wall mosaic.
Kamaba (釜場): behind the bath area, it’s the boiler and water pump system machinery room. Some uses gas, others electricity or even wood.
Entotsu (煙突): chimney