That little rolling brook in your back yard is a stream. If it starts rising and threatens to flood, your father might let out a stream of expletives. A stream is a steady flow of something.
As a verb, stream means to flow out. If water streams from a faucet, it is pouring out. After a concert people stream out of a stadium and into the parking lot. On the web, you'll hear about something connected with music and video called streaming. This means that instead of having to download it to play, it is sent through your computer to listen to or watch, sort of like the way radio and TV work.