The way the router works is kind of like this … simplified so not 100% accurate.
INTERNET
Router Outward facing IP address provided by FIOS (99.99.99.99)
Plus DNS addresses to find stuff on the intertubes
Router Inward facing (192.168.1.1)
Your devices 192.168.1.xxx (or other default configs)
The router will let any of the internal devices talk to each other without going out. (i.e. if the device is in the 192.168.1.xxx list, it knows it doesn’t have to send traffic out to the world). But, if a device tries to find something that isn’t in the local device list, the gateway address will pass it up to the outward facing part of the router and send the request on.
Since your iPad and PC are inside the routers local address list, they should easily find each other and sync up.