2004 Ford Taurus not moving

Transmission problem
2004 Ford Taurus Front Wheel Drive Automatic 78000 miles

Last night I drove my son back to college, everything was fine. On the way home I stopped and got gas. Exited the station, drove up to the light and waited to turn. When the light changed and I stepped on the gas the car would not move. I tried shifting into all the gears and nothing. The engine would rev and the shift will move up and down but it wont go into any gear. What could cause this? I am being told everything from the transmission, the linkage, the timing belt, etc.
Thank you