Who Is The Buddha?

A Buddha is a person who has developed all positive qualities and eliminated all negative qualities. Buddha was an "ordinary" human like you and me before he became enlightened. Enlightenment is compared to awakening, as a person suddenly experiences a complete transformation of body and mind from sleeping to waking up. One could say that a Buddha represents the very peak of evolution, as  he/she is omniscient or all-knowing.

The first buddha is said to have been gautama buddha. There are three kinds of buddha, sammasambuddhas, paccekabuddhas and savakabuddhas.    
the first kind attain buddhahood then teach others. Gautama buddha was this kind. The second type attain nirvana but are unable to teach it to others like the first kind. They're also known as silent buddhas. And the last sort achieve nirvana after hearing  the teaching, directly or indirectly, of a   sammasambuddha.