This document provides an overview of Spanning Tree Protocol (STP) and Rapid Spanning Tree Protocol (RSTP), which are protocols used to create a loop-free topology in Ethernet networks. It describes the goal of preventing broadcast storms by eliminating loops. Key aspects of STP covered include the root bridge, port roles (root port, designated port, non-designated port), BPDUs, path costs, and how STP establishes a loop-free topology for bridged network segments. The document also provides standards information for various STP implementations.