Polkadot is a decentralized, open-source cloud platform that provides scalability and interoperability features to various smart contracts. The project has been developed by Web3 Foundation based on their experience with the Ethereum blockchain. The main use case of Polkadot is to power decentralized applications and smart contracts. Polkadot has its own native currency, DOT, which is used to pay for transaction fees on the network.

The main difference between Polkadot and other cryptocurrencies is its focus on interoperability. The protocol was designed to allow different blockchain protocols to connect with each other, known as parachains. A parachain is basically a blockchain that is connected to the main relay chain of Polkadot but doesn’t need its own consensus protocol because it uses the security of the relay chain. This means that parachains can scale horizontally while still benefiting from all of Polkadot's features.

The project has received backing from some major cryptocurrency exchanges and investors. However, it is still in development and is not yet live on mainnet.