(Sanskrit) n. “awakened one, enlightened, sage, knowledge, wise one.” adj. “awake, conscious, wise, intelligent, expanded.”
Commonly used to refer simply to the Buddha Shakyamuni (the “founder” of Buddhism), the term Buddha is actually a title. There are a vast number of Buddhas, each at different levels of attainment. At the ultimate level, a Buddha is a being who has become totally free of suffering. The Inner Being (Hebrew: Chesed; Sanskrit: Atman) first becomes a Buddha when the Human Soul completes the work of the Fourth Initiation of Fire (related to Netzach, the mental body).
One of the Three Jewels (Tri-ratna), which are Buddha (the awakened one, our own inner Being), Dharma (the teaching he gives to perfect us), Sangha (the community of awakened masters who can help us awaken).
The historical Buddha Shakyamuni is a very great master who continues to aid humanity. Nevertheless, he is not the only Buddha.
"Much has been said of the Buddhas. There is no doubt that there are Contemplation Buddhas and Manifestation Buddhas. Manifestation Buddhas are creatures who dominated the mind, who destroyed the ego, who did not let negative emotions enter their hearts, who did not create mental effigies in their own mind nor in the minds of others. Let us remember Tsong Khapa who reincarnated in Tibet; he was the Buddha Gautama previously. The Buddha of Buddha Amitabha is another thing, his true divine prototype. Amitabha is the Contemplation Buddha, and Gautama, we could say, is the Manifestation Buddha, the worldly Buddha or Bodhisattva. We cannot deny that Amitabha expressed himself brilliantly through Gautama. We cannot deny that later Amitabha sent Gautama (the Bodhisattva or worldly Buddha) directly to a new reincarnation. Then he expressed himself as Tsong Khapa. These are Contemplation Buddhas, they are masters of their mind, creatures who liberated themselves from the mind. The Lords worship the Great Buddha that we also know as the Logos and they pray to him." - Samael Aun Weor from the lecture entitled Mental Representations
"We know very well that Atman-Buddhi is the Inner Buddha, the Buddha, the Innermost; this is how it is written in the Sanskrit books. Now then, we know that Christ is the Second Logos; since the First Logos is Brahma, the Second is Vishnu (the Son) and Shiva is the Third Logos (the Holy Spirit). Therefore, the Inner Christ, evidently and within the levels of the Being, or better said, within the levels of our Superlative and Transcendental Being, is beyond our Inner Buddha, yet they complement each other. Two types of Buddhas exist; yes, we know this. There exist the Transitory Buddhas and the Permanent Buddhas. A Transitory Buddha is a Buddha who still has not achieved within himself the incarnation of the Inner Christ. A Permanent Buddha or Buddha of Contemplation is a Buddha who has already Christified himself, a Buddha that has already received the Inner Christ within his own internal nature. This type of Buddha is a Buddha Maitreya, since it is a Buddha who incarnated the Inner Christ (this is how the term “Maitreya” should be understood). So, Buddha Maitreya is not a person: Buddha Maitreya is a title, a degree, which indicates any given Buddha who already achieved Christification." - The Esoteric Path
"The Buddha appears in the world so that sentient beings may obtain the gnosis that he himself obtained. Thus, the Buddha's demonstrations of the path are strictly means to lead sentient beings to buddhahood." - The Fourteenth Dalai Lama [http://www.dalailama.com/page.22.htm]