They are the rooms in a school/university where each particular subject is taught.

It usually relates to a school or university. Each classroom has a different purpose the history room is for teaching and learning history. Geography room for teaching and learning geography. The music room is for teaching and learning music. The English room is for teaching and learning English.

Think of them like this "a room for history" "a room for geography". these combination tell you what the room is for. other examples are bedroom, living room, dining room, bathroom etc.