Buddha is enlightened(in pali / bodhi) person who has no craving, hatred, or ignorance in his mind, who is free from bondage and has no attachments, and who has attained mastery over the truth.
The 4th stage of enlightenment is Arahant = Buddha
There are three types of buddha.
3 types of Buddha
sammāsambuddha
The perfectly Enlightened person: one who has the ability to complete enlightenment on their own and lead others to enlightenment.
In this world, it is said that up to five sammāsambuddhas can appear, and Gautama Buddha is the fourth sammāsambuddha.
paccekabuddha
The Enlightened person: one who attains enlightenment through his own efforts without listening to the teachings of Buddha, but cannot preach truth and save people from suffering.
They are enlightened and liberated without being known to others, and disappear without being known to others.
anubuddha
The Enlightened person (Arahant): one who has perfected his enlightenment according to the teachings of sammāsambuddha.