Young Blonde Girl In The Room With A Chair Posing At The Door

Architectural doors have numerous general and specialized uses. Doors are generally used to separate interior spaces (rooms, closets, etc.) for privacy, convenience, security, and safety reasons. Doors are also used to secure passages into a building from the exterior for reasons of safety and climate control.
Doors also are applied in more specialized cases:
A trapdoor is a door that is oriented horizontally in a floor or ceiling, often accessed via a ladder.
Blast-proof doors are constructed to allow access to a structure but also to provide protection from the force of explosions.