(to my understanding) you're telling the gateway to direct external traffic on a given port to a specific address in the internal network. it doesn't matter what address you have on the external network; your local address is how your router directs traffic, regardless of its origin, to your device.
this is correct. in the port forwarding menu, you're telling the router which IP on your
internal network will have the server running. If this is your main computer and not some other server, then it's the ip you get from running ipconfig in the command prompt.
once someone connects to your
external IP (your public one that says where you are in the world) for your server, it'll direct their traffic to your router, which will check the port forwarding schedule and send it to whatever subnet IP address you specified. Mine, for example, is always going to be 10.0.0.14, while my public IP changes all the time because I use a VPN. I always port forward to 10.0.0.14 because that's where my router knows my computer is in my home network (static IP assignment), but this IP should be different for you :p
