This one is quite something new to me, This mesh technology was introduced by Google in order to improve the reliability and signal range at home. Now how does this thing works? One of the modules is connected to the modem router via LAN cable, and the other one is placed to a place where wifi signal is bad or non existent at all because of all the walls and obstructions along the way. Remember that signal travels thru air and once there is a thick wall, it nullifies the signal.
So how different is that from your wifi repeater? This one works like a mesh, so you might need to buy some more nodes to connect to each other in order to expand the range, whats best is that the expanded range maintains the same speed gathered from the modem router. Example: If your subscribed speed is 100 MBPS, then you should get at least close to that speed from your mesh. if you are using a repeater, then you should be getting just half of the subscribed speed, lets say just 50MBPS.