HD Wallets refer to crypto-currency wallets that use the Hierarchical Deterministic (HD) protocol. With HD Wallets, a single master seed requires 12 mnemonic phrases. These deterministic wallets are built on a particular algorithm and seed. One of the biggest advantages of using an HD wallet is that keys can only be generated via a specific master private key. In other words, all third-party users with a public key can only view the wallet balance, without making any transactions.