Yes the hotel "terminology in Europe is somewhat different from the States. Here are the most common ones:

En suite: bathroom/toilet is part of the bedroom, i.e. you have a private bathroom as opposed to a shared one.

Single: with a single bed only

Double: in general with a standard double bed

Twin: with two standard single beds, but sometimes (ask) there are two double beds in the room

On this site you will find the standard bed sizes compared for US, UK, Australia and Europe: http://interiordec.about.com/od/buyingabed/a/a_bedsizes_2.htm

Bathrooms in UK/Europe don't necessarily have a bath and a shower. So if you would like to have a bath in the room as well as a shower, you will need to specify this on your reservation.

Regards, Bard Vos Arroyo de la Miel