Yes, Milo Wifi can indeed be classified as a mesh wifi system based on the way mesh is used in describing distributed wifi systems. This is because each individual Milo unit provides routing functionality, as well as being able to "talk" to each other OR to your existing router.
Milo Wifi can be set up as its own network (still using the internet connection provided by your ISP) to provide your home with two networks, or it can be merged into your existing router's network. The choice is yours.
Don't worry if you get frustrated trying to sort through technical wifi jargon!
Feel free to analyze the alphabet soup of 802.11 standards and all the technical terms that relate to wireless internet, but don't fret if you can't exactly pin down each and every bit of information. Just remember, if you need wifi in places where your existing router can't get to, Milo Wifi knows exactly how to solve that problem.