A static IP address is an IP address that was manually configured for a device, versus one that was assigned by a DHCP server.
It's called static because it doesn't change.
Most routers will just assign internal addresses on a first come first served basis.
The first computer you plug into the router will send out a network request saying “I need an IP address”, and will be assigned 192.168.0.2. Your public IP address is not generally something you can change—it is given to you automatically by your internet provider.
In the following example, we’ve added a DHCP Reservation for the device with the MAC address E0: CB:4E: A5:7C:9D, currently with IP 192.168.0.10.
You can also change the IP address to something new if you like, but you will need to restart the device in order to get the new address. You can keep your special routing rules the same, and if a device or server restarts, it’ll simply be given the same IP next time.
There are two or more fields that need to be filled in to add a new IP address reservation.
First is the hardware MAC address (six pairs of alphanumeric characters), which is unique to every device in the world. You should be able to see your MAC address in the list of current “leases”.
It’s the job of your router to assign a new IP address when a device joins the network and maintain a phone book of who has what number.
A static IP address (also known as fixed IP address) is simply one that doesn’t change.