Promises are very useful in many of the core aspects of Angular. Although they are no longer bound to the core framework service, they still manifest themselves throughout Angular's APIs. The implementation is considerably simpler than Angular 1, but the main rhythms have remained consistent.
You can refer to the code, links, and a live example of this at http://ngcookbook.herokuapp.com/5195 .
Before you start using promises, you should first understand the problem they are trying to solve. Without worrying too much about the internals, you can classify the concept of a Promise into three distinct stages: