Polkadot is a network built to let many separate blockchains work together. It is a decentralized, nominated proof-of-stake platform with smart contract support, and its main job is interoperability: letting independent chains exchange data and assets directly, without routing everything through a central party. Most blockchains run as islands that cannot easily talk to each other. Polkadot is designed to be the link between them.
The design centers on two parts. At the core sits the relay chain, which provides shared security and coordinates the network. Attached to it are parachains, separate blockchains that run side by side and plug into the relay chain. Because the relay chain secures all of them, a new parachain does not have to build its own validator set from scratch; it inherits the security of the wider network. Each parachain can be tuned for its own purpose, whether that is payments, gaming, identity, or something else, while still passing messages and value to the others through Polkadot.
Polkadot was created by Gavin Wood, a co-founder of Ethereum, along with Robert Habermeier and Peter Czaban. Two organizations sit behind it. The Web3 Foundation, set up in 2017, supports the wider research and the token, and Parity Technologies builds much of the core software. The mainnet launched in May 2020 under a proof-of-authority model, and by June 2020 the network moved to its nominated proof-of-stake design. Parachain functionality went live in December 2021, the point at which multiple chains could begin running and connecting to the relay chain at once.
The native token is DOT. It does several jobs across the network. Validators produce blocks and keep the relay chain running, while nominators stake DOT to back validators they trust, which is what the nominated part of nominated proof of stake refers to. DOT also carries governance rights, giving holders a say in how the network changes over time, and it is used to support parachains in securing a slot on the relay chain.
Polkadot's role in crypto is as one of the better-known attempts to solve the problem of blockchains that cannot communicate. Rather than asking every project to live on one chain, it offers a shared base layer that many specialized chains can connect to. That is why it is often grouped with the small set of networks aimed at tying the wider field together rather than competing as a single application platform.