Zones

Zones are one of the new concepts that have been introduced in Angular. The concept of Zones was migrated from Dart to JavaScript.

The main reason why a lot of developers were attracted towards Angular initially was by its Auto-magic Data Binding among other things. This was achieved using scopes in Angular 1.x. In Angular 2, we are using Zone.js (https://github.com/angular/zone.js) to achieve the same.

Whenever there is a change in the data, Angular updates the appropriate stakeholders (variables, interfaces, providers, and so on) with new data. Angular can track all synchronous activities quite easily. But for change detection in asynchronous code, such as event handling, AJAX calls, or Timers, Angular 2 uses Zone.js.

To know more about zones, how they work, and change detection in Angular, check out Zones in Angular: http://blog.thoughtram.io/angular/2016/02/01/zones-in-angular-2.html and Angular change detection explained: http://blog.thoughtram.io/angular/2016/02/22/angular-2-change-detection-explained.html.