Polkadot is a blockchain that has a very clear and innovative goal: to function as an interconnection hub for the various existing blockchains.
To this end, Polakadot has two main functions.
The first is to function as a data transmission and processing blockchain. This would allow Polkadot to be an extra layer of scalability for other blockchains.
And the second is independent operation through its own blockchains. Which gives Polkadot the ability to run its own Smart Contracts and host Decentralized Applications (DApps).
Polkadot uses Parachains technology, which allows it to create sub-chains with independent operation from the main chain, known as Relay Chain.