RSTP vs STP
In application software v6.0 and later, the Rapid Spanning Tree Protocol (RSTP) replaces the 802.1D Spanning Tree Protocol (STP). STP is pretty slow at recovering from a failure in the network. RSTP was created to decrease this recovery time.
When a switch is running RSTP, a port can change from blocking to forwarding more quickly than when the switch is running STP. This decrease in transition time makes it possible for RSTP to recover more quickly from failures in the network.
In STP, a port that is blocking must change to listening and then learning before it can change to forwarding. Normally, a port remains in the listening state for 15 seconds and in the learning state for 15 seconds. With these two 15-second delays, a port normally takes 30 seconds to change from blocking to forwarding. This 30-second transition time results in a 30-second loss of traffic, which is not acceptable in many of today's networks.