In early Indian Buddhism and in some later traditions—including Theravada, at present the major form of Buddhism in Sri Lanka and other parts of Southeast Asia—the term bodhisattva was used primarily to refer to the Buddha Shakyamuni (as Gautama Siddhartha is known) in his former lives.
The stories of his lives, the Jatakas, portray the efforts of the bodhisattva to cultivate the qualities, including morality, self-sacrifice, and wisdom, which will define him as a buddha. Later, and especially in the Mahayana tradition—the major form of Buddhism in Tibet, China, Korea, and Japan—it was thought that anyone who made the aspiration to awakening (bodhicittotpada)—vowing, often in a communal ritual context, to become a buddha—is therefore a bodhisattva. According to Mahayana teachings, throughout the history of the universe, which had no beginning, many have committed themselves to becoming buddhas. As a result, the universe is filled with a broad range of potential buddhas, from those just setting out on the path of buddhahood to those who have spent lifetimes in training and have thereby acquired supernatural powers. These “celestial” bodhisattvas are functionally equivalent to buddhas in their wisdom, compassion, and powers: their compassion motivates them to assist ordinary beings, their wisdom informs them how best to do so, and their accumulated powers enable them to act in miraculous ways.