A brief excerpt from 28 Buddhas a 19 June, 2015 entry on the British Library website
In Theravada Buddhism, ‘Buddha’ refers to one who has become enlightened through their own efforts and insight. A Buddha is someone who has realized the enlightenment that ends the cycle of birth and death and which brings liberation from suffering. In the Pali canon, it is stated that Buddhas have appeared in the past and will also appear in the future. There were also numerous enlightened Buddhas who arose in earlier world-cycles and who preached the very same Dhamma that gives deliverance from suffering and death to all mature beings. The names of these 28 Buddhas are religiously preserved by Buddhists, together with their age, their stature, the names of the trees under which they obtained Enlightenment, their country, and the names of their father and mother. They all have two chief disciples to assist them in their mission. Every Buddha has always obtained the supreme intelligence under the shadow of a certain tree.
All these 28 Buddhas were born into royal families or rich Brahmin families. When they had seen the four signs – an old man, a sick man, a corpse, and an ascetic – they renounced worldly life and left home. They engaged in meditation on mindfulness until they attained Enlightenment. At the request of God Brahma, they preached their first sermon to those who followed them.
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Image: Taṇhaṅkara Buddha attained Enlightenment under a Rukkaththana tree. British Library, Or. 14823, f. 1. –
Theravada Civilizations 