Observables are a key part of reactive programming, which is a programming paradigm that emphasizes the propagation of changes and asynchronous data streams. In simple terms, an observable is an asynchronous data stream that can be observed and acted upon.
In Angular, observables are a fundamental part of the RxJS library, which is used to implement reactive programming concepts. An observable can emit multiple values over time, and each emitted value is wrapped in an event-like object called a notification. Observables can emit three types of notifications: next, error, and complete.
The next notification is emitted when a new value is available, the error notification is emitted when an error occurs, and the complete notification is emitted when the observable completes its stream of values. Observables can be used to handle asynchronous operations, such as HTTP requests or user events, and to provide a way to handle these operations in a reactive and scalable way.
Observables are often used in Angular for handling data streams in components, services, and directives. They provide a way to manage data streams in a declarative and composable way, which can help to simplify complex data operations and reduce the amount of code needed to handle them. Overall, observables are a powerful and flexible tool for building reactive applications in Angular.