Gassho - is both a hand position and a term of greeting and salutation. As a hand position the palms are placed together with the fingers pointing upwards with the joined hands positioned in front of and touching the sternum. In some traditions the joined hands are place directly in front of the face. When used as an expression verbally the hand position is implied. Gassho is an expression of respect, appreciation, and prayer.
"It should be noted that the gassho and the bow are common to all sects of Buddhism, both Mahayana and Theravada. These two gestures date from the earliest days of Buddhism, or even earlier than that, and they have moved from India throughout the Orient, finally arriving recently in the Western world.
When Shakyamuni Buddha's enlightenment occurred, he went to see five of his former comrades with whom he had practiced various austerities and spiritual disciplines prior to his enlightenment. These five men, who were very devout monks, felt that their companion had gone astray when he abandoned their customary practices. "Come," they said to each other, "Let's not pay any attention to poor Gautama, he no longer is one of us." They were dismayed to find that he had seemingly stopped his spiritual practices, going so far as to even drink milk and take a bath (two forbidden acts according to their tradition). They could not understand why he seemed only to sit quietly, doing nothing of any value.
But when the Buddha approached them, it is reported that these five monks were so struck by the transformation of their former friend, by his serenity and the radiance of his personality, that they spontaneously placed their palms together and greeted him with deep bows. Perhaps it is a little misleading to say that they greeted HIM. More accurately, it should be said that they were bowing not to their old friend Gautama, but rather to the Buddha -- the Enlightened One." (from Wikipedia)