Where my IP address primer when I need it..
Anyway..here's the fastest explanation...
There are 2 different kinds of IP addresses. Public and Private. Public IP addresses are unique across the internet to allow for packets to be routed from/to the right place. Every device on the Internet needs one to operate. However, if you wanted to connect half a dozen devices, as an example, to the Internet from your home, you would need unique IP addresses for each of those. Now imagine that every person did this and suddenly we'd be out of IP addresses.
To get around this, there are Private IP addresses that only work within a small network. These IP addresses use the 192.168.x.x, 172.16.x.x, 10.0.x.x IP address ranges. All of them talk to a router that is sitting between the devices and the Internet. The router gets the unique public IP address and deals with all the local devices with their private IP addresses.
So when all of your computers/devices go out onto the Internet, they are known by your public IP, but inside your house, they are known by their private IP.
Anyone from the Internet who does a scan will get your public IP address which can be used to determine your geographical location, ISP and other relevant information. With a warrant, they can figure out WHO has been assigned the IP address.