Grandma:
Remember in the old days where you picked up the can with the string, pulled it tight, and hollered into it (yes, like the Progresso commercials)?
Well, this is a new fangled way of doing the same thing.
Seriously, does your Grandmother even understand the internet? Or Internets as the case may be?
Try this:
Grandma, a company called Google, which controls the world, decided to give everyone the ability to call free over the internets (plural intended). They did this because their goal is to someday control all aspects of our lives. Then a company called OBiHai (yes Grandma, the name is weird) made a white box that lets us plug our phones into it and use Google Voice, so we don't need a computer. This allows you to make calls to all your friends, talk for hours and hours, and all for free - leaving more money available for you to lose at Bingo or the bus trips to Atlantic City.