At their core, all three of them, PGPM, PGDM and MBA are the same. They focus on educating students about the moving parts in management. The difference between them is more superficial rather than fundamental.
PGPM (Post Graduate Program in Management) is a certification program, It doesn't rquire any approval from AICTE or other accrediting bodies.
PGDM (Post Graduate Diploma in Management) is a diploma program certified by AICTE.
MBA (Masters in Business Administration) is a degree program offered by a college affiliated to a a recognized university or by the university itself.