Parachains and legacy blockchains are both types of distributed ledger technology, and they have some key differences. Legacy blockchains, such as Bitcoin (BTC), use a proof-of-work (PoW) consensus mechanism to secure the network and validate transactions. On the other hand, Parachains are blockchain networks built on top of the Polkadot platform and use a PoS consensus mechanism. One of the main differences between the two is that parachains are designed to be scalable and interoperable, allowing for fast and efficient transaction processing and enabling the exchange of data between different blockchain networks. Instead of relying on each individual chain to secure the network, using the shared security of the Polkadot platform, multiple parachains can operate concurrently on the same network, potentially enabling much higher transaction throughput than is possible on legacy blockchains.