Closet

A closet (especially in North American usage) is an enclosed space, with a door, used for storage, particularly that of clothes. "Fitted closet" are built into the walls of the house so that they take up no apparent space in the room. Closets are often built under stairs, thereby using awkward space that would otherwise go unused.
A piece of furniture such as a cabinet or chest of drawers serves the same function of storage, but is not a closet, which is an architectural feature rather than a piece of furniture. A closet always has space for hanging, whereas a cupboard may consist only of shelves for folded garments. The word "wardrobe" can refer to a free-standing piece of furniture (also known as an armoire), but according to the "Oxford English Dictionary", a wardrobe can also be a "large cupboard or cabinet for storing clothes or other linen", including "built-in wardrobe, fitted wardrobe, walk-in wardrobe, etc."
Other uses of the word.
In Elizabethan and Middle English, "closet" referred to a small private room, an inner sanctum within a much larger house, used for prayer, reading, or study. 
The use of "closet" for "toilet" dates back to 1662. In Indian English, this use continues. Related forms include earth closet and water closet (W.C. or flush toilet). "Privy" meaning an outhouse derives from "private", making the connection with the Middle English use of "closet", above.
Closet tax question in colonial America.
Though some sources claim that colonial American houses often lacked closets because of a "closet tax" imposed by the British crown, others argue that closets were absent in most houses simply because their residents had few possessions.
Closet organizers.
Closet organizers are integrated shelving systems. Different materials have advantages and disadvantages: