What is event emitters in Angular 2 and how it works?

Any change that occurs in the component gets propagated from the existing component to its children. If this change needs to be reflected its parent component, you can use using Event Emitter api to emit the event.

EventEmitter is class in @angular/core module that is used by directives and components to emit events.

@output() somethingChanged = new EventEmitter();

You can use somethingChanged.emit(value) to emit any event. You can do this in setter when the value is changed in the class.