The number of unique addresses that appeared for the first time in a transfer on a Polkadot Parachain. A parachain is an application-specific data structure that is globally coherent and can be validated by the validators of the Relay Chain. They take their name from the concept of parallelized chains that run parallel to the Relay Chain. Most commonly, a parachain will take the form of a blockchain, but there is no specific need for them to be actual blockchains.