IPAD's when purchased come in two flavors for connectivity.
1. WIreless LAN Only
2. WIreless LAN and 3G/4G(Cellular)
By default your IPAD will connect to any wireless LAN network in which you are permitted to connect such as your FIOS Wireless LAN as you have in your home. When you travel outside your home and don't have Wireles LAN connectivity that is where the Cellular connection comes in handy. You can always check the area you are in for free wireless LAN.
You probably saw around a $20 increase in your cell phone bill which would be for the IPAD. Folks like to have that connect anywhere for that $20 per month. If you don't have Cellular you will only connect when in a wireless hotspot or at home on FIOS (or any other wireless LAN).
FIOS Internet is generally not avaiable outside the home except in a few places that Boingo is avaiable such as Airports. Generally FIOS Wifi is not something you should count on using unless you travel a lot.