The pile is often sheared in order to achieve different textures.
The pile usually consists of twisted tufts which are typically heat-treated to maintain their structure.
The term "carpet" is often used interchangeably with the term "rug", although the term "carpet" can be applied to a floor covering that covers an entire house, whereas a "rug" is generally no bigger than a single room, and traditionally does not even span from one wall to another, and is typically not even attached as part of the floor.
Knotting by hand is most prevalent in oriental rugs and carpets. Pile carpets, like flat carpets, can be woven on a loom.
Both vertical and horizontal looms have been used in the production of European and oriental carpets.
On a knotted pile carpet (formally, a "supplementary weft cut-loop pile" carpet), the structural weft threads alternate with a supplementary weft that rises at right angles to the surface of the weave.