On the Ethereum network, a sidechain refers to a separate and independent blockchain running in parallel to Ethereum Mainnet. Sidechains run their consensus algorithm and connect to Ethereum Mainnet via a two-way bridge. Ethereum sidechains are based on the Ethereum Virtual Machine (EVM), and the sidechain smart contracts run Solidity.
NFT Term
Sidechains
Definition of Sidechains from the NFTguild.com glossary.

