The tie (or necktie) is a long piece of cloth worn for decorative purposes around the neck or shoulders, resting under the shirt collar and knotted at the throat.

The standard length remains 57" (145 cm), though 2008 and 2009 saw a return to narrower ties. While ties as wide as 3.75 (9.53cm) are still available, ties under 3" (7.62 cm) in width also became popular, particularly with younger men and the fashion-conscious.

Here are figures dispaing five main manners used to knot neckties. The simplest, the four-in-hand knob, may be the most common.

Sources: http://en.wikipedia.org/wiki/Necktie