What is spanning tree protocols?

Spanning Tree Protocols (STP) are network protocols that build a loop-free logical topology for Ethernet networks. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them. STP allows a network design to include spare (redundant) links to provide automatic backup paths if an active link fails, without the danger of bridge loops, or the need for manual enabling/disabling of these backup links. It is commonly used in network switches to prevent loops in a network topology.