NgRx is a reactive state management library for Angular applications, based on the principles of Redux. It leverages the power of RxJS (Reactive Extensions for JavaScript) to manage the state of the application in a predictable manner. NgRx provides a set of tools for handling state, side effects, and routing in Angular applications, and it works seamlessly with Angular’s dependency injection system.

In Angular, both Observable and Subject are part of the Reactive Programming paradigm, leveraging the RxJS library. However, they serve different purposes and have different behaviors.

In TypeScript (and JavaScript in general), arrays are reference types. This means that when you assign an array to another variable or pass it into a function, both variables or parameters reference the same memory location.