@bot @olmitch @meso Your device has to talk to your router first before it can talk to the outside world, hence the term "default gateway". When you make a request for a website from a device, It knows this device, from a specific IP and port, asked for a specific IP and port outside the network (remember, DNS is not a factor here in routing).

Your router may either preserve the device's source port or rewrite it altogether and use its own in place (It doesn't matter, because that website is seeing the router, on your public IP, make the request). Either way, it knows, and because it knows, it can get the traffic to the correct spot.