One fundamental belief of Buddhism is often referred to as reincarnation -- the concept that people are reborn after dying. In fact, most individuals go through many cycles of birth, living, death and rebirth. A practicing Buddhist differentiates between the concepts of rebirth and reincarnation. In reincarnation, the individual may recur repeatedly. In rebirth, a person does not necessarily return to Earth as the same entity ever again. He compares it to a leaf growing on a tree. When the withering leaf falls off, a new leaf will eventually replace it. It is similar to the old leaf, but it is not identical to the original leaf.
Alaya-vijnana is the basic source of life. As it comes into contact with different conditions and circumstances, it gives rise to various mental formations and actions, hence karma. The seeds of karma are [in turn] stored in this giant warehouse of alaya-vijnana. The relative abundance of the good or bad karma in this giant warehouse then determines the direction of the next rebirth. When a being dies, the alaya-vijnana is the last to leave the physical body. When a being is reborn, the alaya-vijnana is the first to arrive in the next body. It is the core of rebirth.