A protocol and framework for creating a sidechain or Layer 2 blockchain, both of which run parallel to and interact with the Ethereum network. As of August 2022, there are three live Polygon networks, one test network and three networks in development. More than 1,500 decentralized apps (dApps) have been developed for Polygon chains. The Polygon website touts these implementations as "a suite of Ethereum scaling solutions."
Polygon "secured chains" use a pool of professional validators, and Polygon "stand-alone chains" handle their own security and pool of validators. See Ethereum
and Layer 2 blockchain