Polkadot network architecture

Polkadot is a multi-chain protocol built to knit many blockchains into one secure fabric, and it exists because isolated chains cannot scale or talk to each other effectively. The network centers on a Relay Chain that provides finality and shared security for every connected chain. Parachains are independent blockchains that plug into the Relay Chain and can be specialized for a clear purpose. Parathreads offer the same benefits as parachains but on a pay-as-you-go basis for projects that need intermittent connectivity. Bridges link this ecosystem to outside blockchains and enable token and message flows between different networks. Polkadot secures all of this with a consensus called Nominated Proof of Stake, which asks token holders to stake and to choose validators they trust. Validators run the nodes that finalize blocks on the Relay Chain and they must stay online and honest to avoid penalties. Nominators lock tokens to back validators and they share in rewards when their choices perform well. Collators gather transactions for each parachain and build block candidates that they pass to validators for validation. Fishermen watch for bad behavior and report misdeeds so the network can punish cheaters. The reward and punishment system is relentless; honest participants earn yields and malicious or offline actors lose a portion of their stake through slashing. Nominators can support multiple validators at once, up to a fixed limit, and particular reward math means that each active validator slot pays out equally based on the smallest stake in that slot. Claiming rewards requires an action from the user or another party who issues the payout, and once a payout for an era is claimed all nominators for that era receive their share. Rewards that are not claimed may only be available for a limited period before they can no longer be claimed. The design aims for scalability by parallelizing work across parachains, for security by pooling validation on the Relay Chain, and for interoperability by using bridges and standardized message formats. This model reduces duplication of security effort and lets developers build focused blockchains without reinventing consensus. In short, Polkadot is a framework that sacrifices neat borders between chains to buy coordination, speed, and a shared immunity against attack, and it forces participants to stay vigilant or pay the cost when they do not.