What are Promises and Observables in Angular? 

While both the concepts deal with Asynchronous events in Angular, Promises handle one such event at a time while observables handle a sequence of events over some time. 

Promises – They emit a single value at a time. They execute immediately after creation and are not cancellable. They are Push errors to the child promises. 

Observables – They are only executed when subscribed to them using the subscribe() method. They emit multiple values over a period of time. They help perform operations like forEach, filter, and retry, among others. They deliver errors to the subscribers. When the unsubscribe() method is called, the listener stops receiving further values.