Buddhism is a dharmic religion and form of spirituality that revolves around certain beliefs and practices - all of which are aimed at bringing the participant closer to Buddhahood - the highest level of spiritual awareness. However, because the religion has gained followers in several different parts of the world (mostly in Asia), the way that Buddhism is practiced has split into several different sects. All of the Buddhist sects believe certain things in common: all accept Buddha as their teacher, use the Four Noble Truths and the Eightfold Path in their teachings, and believe that Buddhahood is the highest attainment.
Most scholars divide the different types of Buddhism into three sections. The first of these is Southern Buddhism, or Theraveda Buddhism. The word Theraveda is a word in the Pali language (thought to be spoken by the Buddha) that means "the Doctrine of the Elders". The biggest aim in the Theraveda practice is to use meditation to train the mind, and to encourage freedom of the mind from suffering. This freedom from suffering will allow you to reach the greatest spiritual goal - Nirvana. Theraveda Buddhism is the only surviving school from the earliest years of Buddhism, and it is mostly practiced today in Sri Lanka, Laos and Cambodia.
The second type of Buddhism that is mentioned is Eastern Buddhism, also known as Mahayana Buddhism. This sect not only teaches the Pali Canon (which is the religious text of Theraveda Buddhism) but also includes additional texts and beliefs. In order to reach Nirvana, Mahayana Buddhists believe that a person must practice universal compassion, which is the altruistic quest of the Bodhisattva to attain the "Awakened Mind" of Buddhahood. Mahayana Buddhism also has a level of mysticism involved. This type of Buddhism is practiced in China, Korea and Japan, as well as parts of other Asian countries.
The third of the different types of Buddhism is Northern or Tibetan Buddhism. Tibetan Buddhism is also considered to be a type of Mahayana Buddhism, but it also embraces other teachings, texts and practices that are not seen in the Eastern type of Mahayana Buddhism. Tibetan Buddhism is also sometimes called Tantric Buddhism or Vajrayana. This type of Buddhism uses both the Mahayana and Theraveda scriptures, as well as a number of Buddhist Tantras - all of which are aimed at attaining Buddhahood in just one lifetime instead of requiring many reincarnations.
While all of the different types of Buddhism have the same goal and same basis for their beliefs, the way that Buddhahood is obtained varies from sect to sect. It is important to understand the way that each sect works before choosing to practice a type of Buddhism.