28 Buddhas
There have been 28 samma-sam-buddhas (teaching Buddhas who rediscover the Dhamma and teach the masses when the Dhamma has died-out), ending in the historical Buddha of our time. The Buddha was not the first Buddha, nor the last.
In most Theravada countries it is the custom for Buddhists to hold elaborate festivals to honor 28 Buddhas.
For example, in various parts of Myanmar, festivals are held to pay homage to 28 Buddhas, especially in the fair weather season.
The twenty eight Buddhas are said to have attained enlightenment from the time Gotama Buddha attained his first definite prophecy (assurance that one will definitely become a Buddha one day) from Dipankara Buddha.
According to most Buddhist traditions, Metteyya (Maitreya, in Sanskrit) is expected to be the next Buddha.
Each Buddha attained enlightenment meditating under a tree.
All of the trees are considered Bodhi Trees but they were not all the same species of tree.
See: Bodhi Tree for the complete list of the trees for each Buddha.
The names of the 28 Buddhas
Taṇhaṃkara
Medhaṃkara
Saraṇaṃkara
Dipankara
Koṇḍañña
Maṃgala
Sumana
Revata
Sobhita
Anomadassi
Paduma
Nārada
Padumuttara
Sumedha
Sujāta
Piyadassi
Atthadassi
Dhammadassi
Siddhattha
Tissa
Phussa
Vipassi
Sikhi
Vessabhū
Kakusandha
Koṇāgamana
Kassapa Buddha
Gotama Buddha
(from the Khuddaka Nikaya, Buddhavamsa) List of the Buddhas