Without getting into the technical side of things.
Normal Windows home edition is to what ever firmware your ISP (Internet service provider) puts on your router to make it play nice with their network.
Open WRT is to cracks knuckles fuck it, ill configure it myself (think Arch linux, or any program/platform where the user is given a bundle of sticks and a phone book of a manual and told “try not to hurt yourself”)
Its a community updated router firmware/software project that gives the user a bit too much control. This allowes people who know what they are doing to make some very secure, free, and complex networks, but also gives you the tools to piss off your ISP or break something.
I was disapponted at that, I spooled up one of those instances a few months back and its federated and is magical. If only I could convince my family to move away from that old group text grumbles in person who cosplays as a sysadmin