Think of a stack like stacking plates in your cupboard.
When loading clean plates, you always put them on the top of the pile of plates.
If you want use a plate would you grab from the center or the bottom of the stack? No!
You would grab the TOP plate.
That is a stack!
Think of a queue like taking your car to the automated car wash.
Each car lines up behind another.
One car at a time goes in, in order, and then goes out of the car wash in the same order as they went in.