IP reservation is the process of assigning a specific IP address to a device, such as a computer, so it receives the same address each time it (re)connects to the network, such as when you restart it ...
The majority of the time, we have no idea what the IP addresses of our devices are. You don't need to know that your phone has an IP address of 192.168.1.12 on your local network in order to use it.
If you are experiencing trouble with your network connection and have it configured to DHCP, figuring out your IP address can be quite a task. Using a Static IP Address helps avert IP address ...