No Stupid Questions

A lot of good answers here, talking about the IP/port combinations used to identify both sides of a connection. But a key thing to understand is that the ports don't need to be the same on both ends. On the Client side, the port number is often assigned just for that connection. (The standards call those "ephemeral" ports.) So, two independant connections from the same IP are differentiated by their client side IP ports.

It should also be noted that NAT works by translating both IP addresses and ports. So if those two connections are coming from behind the NAT and have different internal IPs but the same port, the NAT will translate that to two different ports from the public IP.

The internet is an inter-networking protocol. Your modem/router gets a single IP address to represent the entire network publicly, but it assigns addresses to each device internally. When it receives a packet from the wider internet, it performs a translation to figure out which internal address to route the packet to. There are headers attached to the packet that your router uses to keep track of which internal addresses to send it to. It's kind of like when someone gets the mail for a single family home -- everyone who lives there has the same street address, but you can figure out who's room to take the mail to based on the name on the envelope.

There's two ports involved, the client port and the server port. Multiple clients with different client ports and the same ip can connect to the same server port, but they can't reuse the same client side port. (if necessary routers can remap this on the fly and change the client port as it leaves the network, keeping a list in its "connection tracking" table)

The client port is usually randomly chosen by the OS networking stack, between 1024-65535.

The router keeps track of the client ephemeral source port to map to which private IP it needs to send the return packet. If devices inside the same network use the same source port, destination IP and destination port then something like Dynamic NAT with port overload is used : What it will do is map the port with another ephemeral ports (usually +1) that's free. The router keeps track of all those mappings.

I didn't read everything to be fair but you do not only have destination IP and Port but also source IP and port in which case they're separate connections even if the source IP might be the same.

And that's only the IP connection side, there's also a lot more to it there could be authentication and stuff which makes it also more unique.

its all about the mac address and how that is encapsulated but available at differing parts of the routed networks in transit.