My 2001 ford taurus will not move at all with car on. Can place in all gear & still will not move a inch. What has happen

With the engine running,in park, open the hood. pull the transmission dipstick,located on passengers side,just below the windsheild.the handle may be red,or yellow.pull the dipstick out and read it.the fluid level should always be in the crosshairs or XXXXXX's it has a full reading, at the top of theXXXXX's but only while the engines running and motors warm. it [the dipstick has a cold reading,but more acurate when read warm,and in PARK. always use FOMOCO transmission fluid when adding transmission fluid to your car. that means ford motor company fluid only.[fomoco] is it leaking fluid at all? do you see red fluid anywhere that you park the car? if so,then you have either a bad front or rear transmission seal. either ones a better thing than a bad transmission ,sounds like you're just low on fluid,but i got to ask where the fluid leaked or where it went? suggest that you check for leaks. you may add fluid to your transmission and it moves, but be alert,look for a leak somewhere.thank you for choosing fixya.com