Parachain
An independent blockchain that runs in parallel and leases security from the Polkadot relay chain through a connecting slot.
Polkadot's central relay chain validates a limited number of parachains at once. Each parachain handles its own logic and state but borrows the relay chain's shared validator set for finality, so a small new chain gets strong security from day one. Messages pass between parachains through a built-in protocol.
Slots were originally auctioned, with projects bonding DOT to win a lease for up to two years. Polkadot later moved toward a pay-as-you-go model called coretime. The design trades sovereignty for security: a parachain cannot fork its consensus, because the relay chain decides finality.
Related terms
The base network layer that lets independent blockchains pass messages and spin up their own connected chains.
InteroperabilityThe ability of different blockchains to exchange data and value without relying on a central intermediary.
FinalityThe point at which a confirmed transaction can no longer be reversed or pushed off the chain.
ValidatorA participant in a proof-of-stake network that proposes and confirms blocks, putting staked coins at risk for honesty.