STP is based on an algorithm invented by Radia Perlman while working for Digital Equipment Corporation, and published in the 1985 paper "An Algorithm for Distributed Computation of a Spanning Tree in an Extended LAN.”
STP prevents loops from occurring by configuring a loop-free path through the network using strategically placed "blocking-state" ports
Radia’s spanning tree algorithm (STA) creates a loop-free topology by selecting a single root bridge where all other switches determine a single least-cost path
Radia Perlman