A Japa mala or mala is a set of beads commonly used by Hindus and Buddhists, usually made from 108 beads, though other numbers are also used. Malas are used for keeping count while reciting, chanting, or mentally repeating a mantra or the name or names of a deity. This practice is known in Sanskrit as japa.

There are numerous explanations why there are 108 beads, with the number 108 bearing special religious significance in a number of Hindu and Buddhist traditions.

The 109th bead on a mala is called the sumeru, bindu, stupa, or guru bead. Counting should always begin with a bead next to the sumeru. In the Hindu, Vedic tradition, if more than one mala of repetitions is to be done, one changes directions when reaching the sumeru rather than crossing it.

Source: http://en.wikipedia.org/wiki/Hindu_prayer_beads