Let me say up front I am a complete newb but PeerTube is a very exciting idea to me.
I have a couple of questions.
Are the videos on an instance when « uploaded » only the url to the video not the video itself?
If so, what is happening when the video is uploaded from the users system is that different?
Not sure to understand your sentence, but if you refer to imports, yes, you can import videos via their url.
Sorry for not making myself clear
What I was asking is it only the url address that is used each time the video is played?
hope thats a little clearer
Still not clear but I’ll try anyway 
If you are importing a video in the « Import via URL » feature, PeerTube will download the video at that address, transcode it in a streamable format, store it, and then serve it. So no, that URL is only used once, at the import stage. Then, each time you watch the resulting video on PeerTube, it is served from PeerTube only.
ahhh thank you that was what I was asking so badly