Most houses have several different kinds of doors, each designed to address a particular need. All doors are classified as either exterior or interior models. These two types are differentiated by construction, weather-tightness, weight and related factors that determine whether or not they can survive exposure to the elements.
Typical weather-tight exterior doors include the front entry door, back door, French doors, glass sliders and patio doors. Lighter-weight interior doors are used between rooms, on closets and in similar applications.
A door's function determines it's construction, appearance and operation. If it's meant for security, it has very solid, durable construction and highly effective hardware.
If, in addition to providing access, it's intended to permit natural light or views, it incorporates glass-a French door or glass slider, for example. If ventilation is important, the door may have a louvered construction or a portion that swings open, like the half-acting "Dutch" door.
For simply dividing rooms, a lightweight hollow-core door is often preferred because it's an economical, easy to use solution.
Doors are also distinguished by their action. Though most swing on hinges, some slide along tracks or fold and unfold.
--Don Vandervort
