The Anjali Mudra

Anjali mudra is performed by pressing the palms of the hands together. The fingers are together with fingertips pointing up. The hands are pressed together firmly and evenly. In the most common form of anjali mudra, the hands are held at the heart chakra with thumbs resting lightly against the sternum. The gesture may also be performed at the Ajna or brow chakra with thumb tips resting against the “third eye” or at the crown chakra (above the head). In some yoga postures, the hands are placed in anjali mudra position to one side of the body or behind the back.
The gesture is used for both greetings and farewells, but carries a deeper significance than a simple “hello” or “goodbye”. The joining together of the palms is said to provide connection between the right and left hemispheres of the brain and represents unification or “yoking”. This yoking is symbolic of the practitioner’s connection with the divine in all things. Hence, performing anjali mudra is an honouring of both the self and the other as the gesture acknowledges the divinity of both practitioner and recipient.
(via wikipedia.com)