External and Internal IP

External and Internal IP address serve the same purpose the only difference is in its scope.

An External or Public IP address is used across the entire internet to locate computer systems and devices.

Internet Service Provider(ISP) assigns the external IP address as soon as the computer is connected to the internet.
User has no control over the IP address that is assigned to the computer.
Also any website that you visit will have access to the IP address.
Each website also has an IP address of its own, the DNS will look up the IP address.

The External IP address can be Static and Dynamic.

Static Public IP address doesn't change and is used primarily for hosting web pages or services on the Internet.
Dynamic public address is chosen from a group of available addresses and changes each time one connects to the internet.

An Internal or Private IP address is used inside a private network to locate the computers and devices connected to it.

If computer is connected to a router with default settings that router will automatically assign a local IP address to your computer.
It is hidden from the outside world and used inside your private network.
It can change depending on what other devices are connected to the same network or in what order they are connected.
We can assign devices with specific IP address in the router control panel.
Devices with Private IP address cannot connect directly to the internet. If it is connected it will have public IP as well.

The Internet Assigned Numbers Authority(IANA) has reserved a range of three blocks for private networks.