Qibla is, in general, the direction of Mecca, more specifically the Ka’ba, towards which each Muslim must turn in order to perform the salat validly. In a mosque the qibla is marked by the mihrab. During a journey, a compass may be used to ascertain the correct qibla; in case of necessity, the individual may use his own judgment, or the general direction may be observed.
During the early period of Islam in Mecca, the Muslims prayed facing the Ka’ba, or, according to a alternative account, toward Jerusalem; after the Hijra, for awhile Muhammad directed prayers should be said facing Jerusalem, the qibla or the Jews.
Then after six months Muhammad ordered Muslims to pray facing Mecca. This is made authoritative in the Qur’an: “The foolish will say: ‘What has led them to abandon their former Qibla?’ Say: ‘The East and West belong to Allah…Then turn your face towards the holy Masjid…'” (Qur’an 2. 142-144) It is said these words were revealed to Muhammad during the morning salat at a placed called Quba, or, alternatively, during the noon salat in a mosque known as Masjid al-Qiblatayn (Mosque of the two Qiblas).
The term qibla may also be use more loosely to designate a fixed direction of prayer in any religion. A.G.H.
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, p. 784