In contrast to permisioned blockchain - where participation and access into the blockchain data requires authorisation, a public blockchain such as Bitcoin is completely is free and available to the public. Anyone can join and view its data. Public blockchain adheres to the original Bitcoin Protocol ethos of not having a central authority to overwrite anyone's authority. Public blockchains are resistance to censorship and foreign interference as it has no single point of failure.
On a blockchain, users interact with one another through their addresses, and daily active addresses (DAA) refers to the number of addresses which fulfills the defined activity parameter on a given blockchain.