If you heard about Flux, Redux, MobX (used for React) NgRx and NGXS (used for the latest version of Angular), those are state management pattern or library that acts as a single source of truth for web application's state. AngularJS Store is based on those popular libraries.
AngularJS Store is specially designed for AngularJS application. It will guide you to create a one way data flow in your application (Single Source of Truth). Help you manage your AngularJS application's state into a very predictable way.