What is the difference between Shradh and Pind Daan?

Shradh is the overall ancestral ceremony, encompassing multiple components: Sankalp (the formal vow), Pind Daan (rice ball offerings), Tarpan (water offerings), Brahmin Bhoj (feeding Brahmins), and Daan (charitable giving). Pind Daan is one component within the Shradh ceremony. You can perform Pind Daan as a standalone rite at a specific tirtha, but a complete Shradh ceremony encompasses all these elements. When people say they are going to Gaya for Pind Daan, they typically mean the full Shradh ceremony performed at Gaya.