A car door is a type of door opening, typically hinged on its front edge, but sometimes attached by other mechanisms such as tracks, for entering and exiting a vehicle. Doors most often integrate side windows for visibility from inside the car and can be locked to secure the vehicle.
Exterior side of car door on a 1986 Ford Taurus
Opened front and rear doors on a 1957 Rambler Rebel
Open doors on a Chrysler Airflow
AMC Gremlin two-door with rear cargo hatch opened
A door is a hinged or otherwise movable barrier that allows ingress (entry) into and egress (exit) from an enclosure. The created opening in the wall is a doorway or portal. A door's essential and primary purpose is to provide security by controlling access to the doorway (portal). Conventionally, it is a panel that fits into the doorway of a building, room, or vehicle. Doors are generally made of a material suited to the door's task. They are commonly attached by hinges, but can move by other means, such as slides or counterbalancing.
Stone door in Hampi (India)
A massive door socket from Persepolis (modern-day Iran)
Roman folding doors at Pompeii, from the first century AD, similar with Neoclassical doors from the 19th century
Roman wall painting of an ornate door, in the Villa Boscoreale (Italy), from the first century AD