RxJS, a framework for reactive programming in JavaScript, is particularly useful for writing asynchronous code through the use of Observables, which are integral to Angular's reactivity by converting callbacks into streams of data. The framework enhances performance and modularity while maintaining compatibility with previous versions, introducing key concepts such as Observables, Observers, and operators. Observables serve as data streams that emit multiple values over time, whereas Observers act as listeners that react to these values through methods like next(), error(), and complete(). Operators are functions that transform, filter, or combine data streams, forming complex pipelines. Unlike Promises, which handle a single asynchronous operation and return a single value, Observables offer more robust error handling and can emit multiple values, making them ideal for real-time data and event handling in Angular. The lifecycle of an Observable involves creation, subscription, execution, and destruction, with the subscribe method linking Observables to Observers to execute tasks. The article also highlights practical examples of creating, subscribing to, and executing Observables, contrasting them with Promises, which are limited to a single resolution or rejection event.