Shraddh is the broader term for the entire ritual performed with faith (shraddha) for the ancestors. It includes invocation, honoring Brahmins, prayers, and offerings.
Pind Daan is the central, most crucial part of most Shraddha ceremonies conducted in Prayagraj. It is the specific act of offering the physical pinds (rice balls) that nourish the subtle body of the ancestor. So, when you come to Prayagraj to perform the annual death anniversary ritual or rites during Pitru Paksha, you are performing Shraddha, and Pind Daan is the key action within that Shraddha.