If you have an existing internet router, you could use a WiFi extender to expand your WiFi network. However, while mesh WiFi systems can also be used alongside your current router, they're often used as a full replacement for your existing router and WiFi network.  WiFi mesh satellites (also referred to as nodes or points) act as the mesh extenders in this case, effectively creating a seamless wireless mesh network that's scalable to the size of the space that you need to cover with reliable internet connectivity.