Spanning Tree Protocol (STP) is used to prevent loops from forming on redundant networks. STP uses different port states and timers to logically prevent loops by electing a root bridge and designating root ports on each switch. Rapid PVST+ is an enhancement of STP that provides faster convergence time of less than 6 seconds compared to 50 seconds for STP, while also supporting VLANs to prevent loops between redundant switches in a VLAN.