Is a bull and a buffalo the same?

Yes and No. Yes due to the fact that males of buffalo (and bison) are called bulls, just like with male domestic cattle (that are intact).  No to the fact that the term bull is just a term for the male sex of the Bovidae family (and others like elephants, seals, rhinos, etc), and the term buffalo is a generic term for the wild bovines cousins to the domestic bovine that refer to Asian Water Buffalo (wild and domestic), African Cape Buffalo, and the American Bison.