Tartan is a patterned cloth consisting of criss-crossed, horizontal and vertical bands in multiple colours. Tartans originated in woven wool, but now they are made in many other materials. Scottish Tartans usually represent a Clan whilst Irish Tartans usually represent the County or region where a Clan originated, For example, someone belonging to the Ua Conchobhar Clan would be represented by either the Loch Garman or Uíbh Fhailí Tartan.
Tartan is made with alternating bands of coloured threads woven as both warp and weft at right angles to each other. The weft is woven in a simple twill, two over—two under the warp, advancing one thread at each pass. This forms visible diagonal lines where different colours cross, which give the appearance of new colours blended from the original ones. The resulting blocks of colour repeat vertically and horizontally in a distinctive pattern of squares and lines known as a sett. Tartan is often called "plaid", but in Scotland, a plaid is a large piece of tartan cloth, worn as a type of kilt or large shawl. The term plaid is also used in Scotland for an ordinary blanket such as one would have on a bed.