Current web3 UX very regularly requires dealing with long hexadecimal 0x1234... addresses, which can represent user-owned accounts (EOAs), tokens, multisigs, and all kinds of other smart contracts.

The addresses appear across many dApps and other frequently visited websites such as block explorers.  However, given how long they are, it's an impossible task to expect users to memorise them.  This creates many obvious usability and even security issues for every single web3 user.

Public naming services such as ENS are a partial solution to this, but they only work when privacy is not required.  Some dApps and block explorers offer private address books, but those only work on a per-site (and sometimes per-chain) basis.

In contrast, rolod0x is a fully generalized browser extension which provides users with a completely private, local-only address book which can work on every website and every chain.