"Often referred to as the ""Blockchain of Blockchains,"" Polkadot is a next-gen Layer 0 meta protocol and an open-source blockchain launched in May 2020 to realize the broader vision of a secure, resilient, and fair Web3.
Polkadot unites a network of native purpose-built Layer 1 blockchains called parachains and multiple external blockchains (connected to it using innovative bridging technology), allowing them to operate at scale alongside each other seamlessly.
The parachains and external blockchains can freely interact with each other, making them interoperable. This is a significant shift from the siloed design of conventional blockchains like Ethereum and Bitcoin. Parachains can process transactions simultaneously, reducing the burden on the main chain and offering ease of scalability. They also allow developers to customize their blockchains, allowing them to optimize parachains for specific use cases with their native tokens.
The Relay Chain is Polkadot's central chain, created using the Substrate framework. The Relay Chain is responsible for maintaining Polkadot's shared security, cross-chain interoperability, and consensus mechanism. It has been designed to handle minimum functions, including the network's governance and nominated Proof of Stake (NPoS). All validators are staked on the Relay Chain and confirm transactions from the connected parachains.
The Polkadot ecosystem also has parathreads, which are parachains based on a pay-as-you-go model, making them more affordable. The parachains and parathreads can connect and communicate with external blockchains like Bitcoin or Ethereum through bridges.
The network is secured using the NPoS consensus mechanism. Users can choose to participate in the consensus system as nominators or validators. Nominators can select trustworthy validators to update the network while validators verify transactions. Both nominators and validators stake DOT and receive rewards in return."