VTP Pruning will eliminate unnecessary broadcast traffic on trunk links. If a broadcast comes from VLAN X, and the neighboring switch does not have any access ports in VLAN X, this broadcast will not be forwarded to it, even if the VLAN is allowed on the trunk.
NOTE that this does not prevent a Spanning-Tree instance from being created for the VLAN X on the neighboring switch. If there is a desire to limit the spanning-tree instances on the neighboring switch, manually removing (or as many people call it manually "pruning") the VLAN from the trunk port is the only way to do this.
Reference : CCNP to CCIE RS Transition Kit by IPEXPERT