I Have A Frigidaire Stackable Washer/dryer. The Washer Begins To Fill And The Water Leaks From The Bottom Of The Machine. You Can Hear The Water Dripping In The Machine. What Is Causing The Leak?

Try filling in a bucket of water without starting the washer and see if you hear the leakage. If yes, most likely your tumbler has a crack. Another problem could be the water flowing in the washer might be splashing out either due to the speed of the water flowing in or the tumbler is not aligned properly.
One more cause could be the hose/valve or the waterpump that takes the water out might have a leaking gasket.