Placement is a ballet term used to describe the specific position in space a dancer should have their body, arms, legs, feet, hips, hands, fingers, and so on.
For example, a dancer may be given a correction to work on “placement of your head” if their head isn’t facing the correct direction for a step.
Placement also goes hand in hand with alignment. Often times, if a dancer has poor alignment it may also be because his or her placement is off.