When using the word "Buddha" we generally mean Śākyamuni Buddha, however
the number of past and future Buddhas is, in principle, infinite.
Sources of the various traditions cite different names and numbers of Primordial Buddhas. (see Theravāda list)
The Mahāyana Lalitavistara Sūtra refers to "hundreds of thousands of niyutas of koţis of Buddhas" - an incredibly large number.
Among these countless Buddhas the Lalitavistara Sūtra gives us the Sanskrit names of the 54 following Buddhas.