Hall is a term often used to refer to several different types of room in a house or a building.
This is either a long, narrow room which serves purely as an access to other rooms (also called a corridor or hallway). As an extension of this, the front entranceway or entrance room of the house is also often called the hall because it serves as an access to the main part of the house (also called the entry hall). In office buildings and larger buildings (theatres, cinemas etc), the entry room is generally known as the foyer or the atrium.
Finally, the term hall can be used to refer to some kinds of building in their entirety, for example a Meeting hall, or a Church hall. Again, I suspect this is because the building serves as a gathering place and it is generally a large empty space with minimal furnishings and decoration.