The router will assign the IP addresses on yur network, unless you tell it do to otherwise. Not doing so can wreak some havoc. For example, our MFP and Plotter just "get lost" unless they have a fixed IP address.
I recommend the following:
Fixed Wired Connections (Using a SoHo scenario - House with small home office as a base, plain home easier):
192.168.1.2 - Something everyone depends on like a cell phone MicroCell should go 1st
192.168.1.3 - Main PC, data or multimedia server, one where everyone backs their stuff up to ...
192.168.1.4 - Office PC
192.168.1.5 - Office PC
192.168.1.6 - Kid No. 1
192.168.1.7 - Kid No. 2
192.168.1.7 - Kid No. 3
192.168.1.215 - Shared Printer
192.168.1.216 - Network Printer
Laptops, Phones, Game Consoles, TV:
192.168.1.xx (let router assign as needed)
If I don't assign a fixed IP address to the printer / plotter, then no one can find them after a router reboot ... I have to rerun the network scan utility.
Also setting up networked drives / NAS often requires an IP address which of course won't work if that IP address changes.
YOUR network addresses will be something similar to the above based upon router defaults. The IP address you get from your ISP That "they change" will look more like
25.198.189.41
To find out what your ISP is giving you... use
https://www.ipchicken.com/