What is a Sidechain?

A sidechain is a separate blockchain that is linked to a main blockchain, allowing for the transfer of digital assets between the two chains. Sidechains exist to provide additional functionality and flexibility of the mainchain, as the sidechain's protocol can follow different rules and characteristics that can enable enhanced utility. These layers make no modifications to the mainchain, which is beneficial for experimentation and testing other innovations. Examples of sidechains for Bitcoin include RSK (Rootstock) and Liquid Network.