A Buddha is any sentient being who has achieved nirvana (broken out of samsara [the "endless wondering," an endless cycle of birth, death and rebirth]).  Their paths to enlightenment might had been different, but their achievement is the same.

A statue of Shakyamuni Buddha in India.  The founder of Buddhism.	Bhaisajyaguru Buddha, the Buddha of Healing.	A statue of Amitabha Buddha in Kamakura, Japan.  The Amitabha Buddha is the Lord of the "Western Pure Land."