Many Buddhists in the Nikaya, Mahayana, and Vajrayana traditions consider there to be three type of Buddha: Samyaksam Buddha (often simply referred to as «Buddha»), Pratyeka Buddha, and Sravaka Buddha.
The three kinds of Buddha
Samyaksam Buddhas (Pali: Samma-Sambuddha, also known in Mahayana as Bodhisattva Buddhas) gain Nirvana by their own efforts, without a teacher for the entire path. They may then lead others to enlightenment by teaching the Dharma in a time or world where it has been forgotten or has not been taught before, because a Samyaksam-Buddha does not depend upon a tradition that stretches back to a previous Samyaksam-Buddha, but instead discovers the path anew. The Historical Buddha, Siddhartha Gautama, is considered a Samyaksam-Buddha.
Pratyeka Buddhas (Pali: Pacceka-Buddha, sometimes called Silent Buddhas) are similar to Samyaksam-Buddhas in that they attain Nirvana, however unlike the Samyaksam-Buddha, they are unqualified to teach. In Mahayana traditions, Pratyeka-Buddhas may remain silent, keeping the discovered Dharma to themselves.
Sravaka Buddhas (Pali: Savaka-Buddhas) gain Nirvana by hearing the Dharma as passed on from a Samyaksam-Buddha. Mahayana and Vajrayana teachings hold that, after attaining enlightenment, Sravaka-Buddhas may also lead others to enlightenment, but cannot teach the Dharma in a time or world where it has been forgotten or has not been taught before, because their enlightenment is dependent on a tradition that stretches back to a Samyaksam-Buddha.
Mahayana & Hinayana
Within the Mahayana tradition, the term Hinayana was coined to indicate those vehicles that lead only to the inferior (hina-) Buddhahood of a Pratyeka Buddha or a Sravaka Buddha. Inferior only because such vehicles do not lead to the full set of qualities of a Samyaksam Buddha. Regardless, this appelation has continued to cause understandable defensiveness from schools and traditions whose main goal is the Buddhahood of a Sravaka Buddha.
The Lotus Sutra (a very early Mahayana sutra) makes the distinction between the vehicles according to the type of Buddha that arises, and all Buddhists agree that a Samyaksam Buddha is superior to a Sravaka Buddha or a Pratyeka Buddha, at least on the basis that only a Samyaksam Buddha can teach the Dharma where (or when) it has not been taught before.
Skillful means rather than ultimate teaching
Significantly, the three types of Buddha appear only rarely in Theravada texts, while in contrast Mahayana literature frequently invokes these three archetypes. However, even within Mahayana traditions, the three types of Buddha do not necessarily correspond to an ultimate teaching, but rather one that fits within a program of skillful means (upaya) or expedient practices. Notably, chapter 3 of the Mahayana Lotus Sutra, compares the three types of Buddha to three vehicles, namely a goat cart, a deer cart, and an ox cart. That discussion is followed by the statement that Buddha «Firstâ€¦ preaches the three vehicles to attract and guide living beings, but later he employs just the Great Vehicle to save them.» That is Mahayana (meaning «greater vehicle» in Sanskrit, a description rejected by Theravadans) transcends the three types of Buddha, rather than corresponding to a method for attaining status as one of the types. In short, while the three-Buddhas archetype remains popular, it is not universal among Buddhists, some of whom maintain a tradition of ekayana, the single vehicle or direct path to awakening.