Polkadot is a global network of blockchains that serves as a foundation for a new peer-to-peer internet by both allowing new blockchains to be built on its framework, as well as enabling existing blockchains to connect, or bridge, to the Polkadot Network.
In simplified terms, individual blockchains are currently incapable of securely transacting and communicating with each other without placing trust in some sort of third party infrastructure.
Polkadot provides a decentralized, trustless framework by which blockchains can bridge to, allowing for secure, trustless communication and transactability under the Polkadot umbrella.
In addition to hosting other blockchains via Bridges, Polkadot is its own protocol that allows for the building of native blockchains, known as Parachains, that reach consensus through a proof-of-stake mechanism.
