Hybrid Blockchains, also called Sidechains, Cross-Chain or Interchain Technology, describe the connection of different Blockchain types and DLT-systems, so that a transfer of assets, tokens, data and communication between different Blockchains is conducted. Especially a communication between Private or Public Blockchains would enable new tradeoffs in the design and allow to combine unique features between both types .
Hybrid Blockchains enable registers and calculations across different frameworks to access, for instance, the data stored on Private Blockchains for certain applications operating in public networks . The access to transactions between different cryptocurrencies is significantly simplified  and the transfers can take place without any delays. Examples of protocols on which Hybrid Blockchains are built are Polkadot, Wanchain and Kadena.
 Polkadot (2020)
 Swan, M. (2015) Blockchain Blueprint for a new economy