What are Streams in Dart?
* The longer-term and Stream classes define asynchronous programming in Dart.
* A stream can be thought of as a series of asynchronous occurrences. It's similar to an asynchronous Iterable in that instead of receiving a future event once you invite it, the stream informs you that an occasion has arrived.
* Streams are formed in various methods, but they have always been used the same way; the asynchronous loop is one.
