The Polkadot blockchain is a multi-chain blockchain that is designed to bundle multiple chains together so that they can be executed in parallel. The goal is for every block on the Polkadot blockchain to contain multiple blocks from other chains. This will enable the network to contain the transaction information from multiple chains and dramatically increase the overall interoperability between different blockchain networks. Polkadot was created by the Web3 Foundation, which is led by Gavin Wood, one of the founders of Ethereum. Polkadot is their flagship project, and aims to solve the issues in the blockchain ecosystem related to disjointed governance and interoperability.
pTokens are digital assets that are transparently pegged to another underlying asset. pTokens serve as a Cross-Chain token wrapper that allows users to more easily transfer value between different blockchains. Users can deposit a certain amount of the underlying asset (such as BTC or EOS) and request the equivalent pTokens that are pegged to them 1:1, such as pBTC or pEOS. Token holders can then take advantage of the Ethereum network by more easily exchanging them into ERC-20 tokens.