No. WiFi and Data Used through VZW are completely seperate. On a tablet [all the ones I have seen and even on most phones now days] you have two different radios you can turn on and off. One is for WiFi. On WiFi you must have a router or WAP [wireless access point] to connect to and that is free and is completely seperate from VZW. You can completely turn off the VZW radio and the tablet will only use WiFi. When you purchase a Data Plan for your Tablet from VZW that operates at a different frequency on a seperate radio in the tablet, if you are out of range of a WiFi connection and/or you are not connected to the WiFi, then if your VZW radio is on your tablet will use data on your VZW data plan and that would be considered VZW Data Usage and will be shown on your account.
End Point: Using WiFi does not count toward Data Usage on your VZW plan.
If I buy a tablet , if I use wifi is it considered data usage?
Not if you are using a home wifi hetwork you wont be charged any data but if you connect with wifi from the tablet to your phones wifi hotspot it will be data use for your phone.
Just figured I would add a bit more information to limit misunderstanding..
Kudo's to that Wildman most definitely! I completely forgot someone could be using a wireless tethering with the MobileHot Spot from VZW. I'll plug the information in about that quickly that the dataplans that allow you to use your phone as a MobileHot Spot are more expensive per unit [$/GB] than just the normal ones.
Excellent add Wildman, thanks for the expansion there.