I agree with Estevan. Chambers are in castles. I can give you one example from modern literature - Harry Potter and chamber of secrets. Such rooms in Hogwarts school were called chambers.

I guess chamber is a room found in old and big buildings like castles and old mansions. We usually don't call the rooms in our houses chambers, do we? Chamber is also a room set for a special purpose. On the other hand, room is a space with four walls found in smaller buildings. A room can be of multipurpose.

Both are basically the same thing, however use the more familiar "room". "Chamber" is used more particularly, and sounds a little florid - there's a sense of status when using "chamber". Basic etymological difference is that "room" is Germanic/Old English originally meaning 'a space'. "Chamber" is from Latin (camera) via Old French, meaning 'a room'. Note modern French "chambre". Though this Latin word has turned up in many European languages. Deep Blue's notes on "chamber" are also worth studying! :)

A room is well defined to everyone, but the word chamber needs a little attention. 1. A room where a person of authority, rank, or importance receives visitors. 2. chambers A room in which a judge may consult privately with attorneys or hear cases not taken into court. 3. chambers Chiefly British A suite of rooms, especially one used by lawyers. 4. A hall for the meetings of a legislative or other assembly. 5. A legislative or judicial body. 6. A board or council.

Chamber is just a fancy way to say room.