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An observable is something to observe and take actions on. The Observer pattern. In Angular, an observable is created - it may be an http call or a call to an internal collection or process. An observable can be mointoring events and may continue after the Observer recieves information. For example, an observable may be monitoring a web socket and supply the messages as they appear. To rerieve the information emitted by an observable one must subscribe to the observable - and in code the Observable has a method subscribe whcih returns the info from the observable.

Observable is part of the RxJS library which must be imported into the angular application. RxJS contains numerous operators which assist in manipulating the stream of data from the observable.. Some are covered here.