Polkadot: Parachains, Sidechains, Bridges and Gateways…
Polkadot is a relatively new cryptocurrency that allows for users to lunch and operate their own blockchains. They do this through a para-chain/relay-chain system. Polkadot is not the only blockchain that has this functions its near cousin Kusama also has these features amidst slight differences.
The relay-chain is the main chain where the data from the parachains are stored using what’s called a collator node while parachains are independent blockchains that share thesame network consensus and security. These chains have their own governance model, their own coins and specific use case. This allows for lower transaction costs, more scalability and interoperability among the chains due to the shared network they use.
Parachains are different from sidechains like Liquid, Rootstock and the shard chains of the ethereum network because they share thesame security network even though they have different functions, whereas sidechains are tied to their parent network like bridges, with aim of improving the overall utility of the parent chain, they also have a different security network from the parent chain and cannot interact with each other like parachains. There is also no limit to the number of sidechains a network can have as against parachains that have a limit.
Parachains are also different from bridges/gateways like the Binance Smart Chain, Bitshares DEX, XBTSX, Chainlink, avalanche, thorchain, etc. because they are essentially blockchain protocols, whereas gateways are simply exchange mediums between two different blockchains, and like sidechains gateways require validation. The security of the gateway comes from its design and how it is built to operate, whereas parachains are secured by a shared network.
In conclusion parachains are completely different from sidechains and gateway/bridges, while one is all about fully functional blockchains built on a secured network, the other is only about maximizing parent chain utility and the latter is all about exchange of asset or data between two completely different blockchains.