How does a Stream really work?

[almostserious]

Hi Im trying to understand how the streams section of the UI actually works.
Am I correct in assuming that this is basically like a port forwarding on my router?

So for example if I previously forwarded Port 8203 to IP 192.0.0.5 in my router, with the Streams I can actually forward the port to my NPM IP and then set the stream to forward this port to the 192.0.0.5 ?
Is that how it works? Or how it should work?
What would be other use cases if this is not how it works?