Early sources say that the Buddha was born in Lumbini (now in Nepal), and that he died around age 80 in Kushinagar (India). He lived around the fifth century BCE, according to scholarship. Buddhism spread throughout the Indian subcontinent in the five centuries following the Buddha's passing, and thence into Asia and elsewhere over the next two millennia.

Indian Buddhism has become virtually extinct, except in parts of Nepal. The most frequently used classification of present-day Buddhism among scholars divides present-day adherents into the following three traditions:

Southern Buddhism, or Theravada (its own usual name for itself), also known as Southeast Asian Buddhism, or Pali Buddhism - practiced mainly in Sri Lanka, Myanmar, Thailand, Laos, Cambodia and parts of Malaysia, Vietnam, China and Bangladesh (Southeast Asia)
Eastern Buddhism, also known as East Asian Buddhism, Chinese Buddhism, Sino-Japanese Buddhism, or Mahayana - practiced predominantly in China, Vietnam, Korea, Japan, Singapore and parts of Russia
Northern Buddhism, also known as Tibetan Buddhism, Tibeto-Mongolian Buddhism, or Vajrayana, sometimes called Lamaism - practiced mainly in Tibet, Mongolia, Bhutan and parts of Nepal, India, China and Russia.
An alternative scheme used by some scholar has just two divisions, Theravada and Mahayana, the latter comprising both Eastern and Northern. Some scholars use other schemes. The term Hinayana, referring to Theravada and various extinct Indian schools, is sometimes used, but is often considered derogatory, and the World Federation of Buddhists recommends it be avoided.

Buddhism continues to attract followers around the world and is considered a major world religion. According to one source, "World estimates for Buddhists vary between 230 and 500 million, with most around 350 million." However, estimates are uncertain for several countries. According to one analysis, Buddhism is the fifth-largest religion in the world behind Christianity, Islam, Hinduism, and traditional Chinese religion. The monks' order (Sangha), which began during the lifetime of the Buddha in India, is amongst the oldest organizations on earth.

In Buddhism, any person who has awakened from the "sleep of ignorance" (by directly realizing the true nature of reality), without instruction, is called a buddha. If a person achieves this with the teachings of a buddha, he is called an arahant. Siddhartha Gautama, the Buddha, is thus only one among other buddhas before or after him. His teachings are oriented toward the attainment of this kind of awakening, also called enlightenment, Bodhi, liberation, or Nirvana.

Part of the Buddha’s teachings regarding the holy life and the goal of liberation is constituted by the "The Four Noble Truths", which focus on dukkha, a term that refers to suffering or the unhappiness ultimately characteristic of unawakened, worldly life. The Four Noble Truths regarding suffering state what is its nature, its cause, its cessation, and the way leading to its cessation. This way to the cessation of suffering is called "The Noble Eightfold Path", which is one of the fundamentals of Buddhist virtuous or moral life.