Glossary
Polkadot
A heterogeneous multi-chain protocol where a central Relay Chain provides shared security to many specialized parachains.
Polkadot, launched in 2020 by Ethereum co-founder Gavin Wood, is a heterogeneous multi-chain network. A central Relay Chain provides shared security and finality (via the GRANDPA + BABE consensus pair) to up to ~100 "parachains" that lease slots via on-chain auctions.
Parachains can be arbitrary application-specific chains (DEXes, gaming, identity, privacy) sharing one validator set. The model predates and contrasts with the Cosmos approach, where each chain provides its own security.