1. PIM-SM is a Multicasting Routing protocol that is independent of the Unicast Routing Protocol. This means that PIM doesnt create its own Unicast Routing table for Reverse Path Checking that the other Multicast Routing Protocols do. Hence its called "Protocol Independent" PIM-SM is also called Sparse Mode protocol as it depends on explicit join messages from the listeners to construct its multicast routing tree. This means that PIM-SM will flood the network with multicast traffic only if the network has one/more interested receivers on it.
2.DVMRP also uses the sparse mode but it creates its own unicast routing table for reverse path forwarding.