A NeoPass account is a unified login system that allows you to access multiple World of Neopets services, including Neopets.com, Faerie Fragments, Tales of Dacardia and future TNT-related projects, with a single set of credentials. It enhances security and streamlines account management.
A Neopets account, on the other hand, is your in-game account specifically for Neopets. It contains your pets, items, Neopoints, progress, and other game-related data.
Essentially, your NeoPass account is the gateway to your Neopets account (and potentially other services in the future), making it easier to manage multiple logins under one system.