There are different protocols for identifying devices in the network. The most common of these is IP (Internet Protocol). Yeah, the name is simple. An IP address is a unique address that identifies a device in network by Internet Protocol. This network can be both a local network and the global Internet.
An IP address is a number of 4 bytes. For human readability, it is written as 4 numbers separated by a dot.
Each device in network can identify another with its IP addresses and send bytes of data directly to this address.
Most likely not. Let's take a look at how the signal travels from your laptop to the global Internet.
In the presented diagram, any device on the Internet will see you with the address 182.24.169.221. This is the address of last device in the network hierarchy.
But here are two options that makes your address unique:
ISPs buy range of addresses for usage. This means that other providers know who owns the addresses. They also know where the equipment using this address is located. Since this equipment is located close to you, the IP address allows you to calculate your location with street accuracy.
Use VPN services. Your visible IP address will belong to vpn service.
In the presented diagram, any device on the Internet will see you with the address 86.220.14.85. VPN service adds one more link in the chain of connections. Remember that VPN hides your ip from chain endpoinds but still knows your IP address.