Stansted is to the north east of London, heading in the vague direction of Cambridge.
It is about 42 miles out, and seems to serve mainly Europe (including Ireland) and some flights to Africa. It is used by a lot of low cost airlines, especially Ryanair.
There is one terminal building, and it is very basic and adequate. We always think it is an airport that is hard to get lost in, and we have never had very long walks to gates.