Bitcoin's blockchain is a digital ledger that stores data happening in the network with three main properties: peer-to-peer, decentralized, and based on cryptography.
Router chain creates infrastructure for developers to create solutions that work on multiple blockchain networks with decentralization, scalability and security in mind.
Polkadot is a next-generation blockchain protocol that unites an entire network of purpose-built blockchains, allowing them to operate seamlessly together at scale.