fishtailing is something that occurs when the back end starts weaving as you’re driving on the road.
drifting is when you have the brakes applied, you aren’t driving forward, and the back end loses traction and the tires spin, and you go in an arc pivoting around the front of the car that is stationary/pivot point.
Drifting is power-on oversteer (assuming rwd).
Think post checkered flag donuts.