UNIT TURN
The first picture is usually the position of the so-called "unit turn" - the simultaneous rotation of the hips and shoulders.
BACKSWING
The second image captures the players' position just around the time when they complete their backswing.
FORWARD SWING
The third image, which is often part of conventional analyzes, captures players' position around the time when they start forward swing to contact point.
CONTACT POINT
On the fourth picture, players are captured just around the time of contact point (near, or just after making ball contact). In exceptional situations, the conventional analysis capture the players right in contact point (with the tennis ball on string bed).
FOLLOW-THROUGH
On the fifth image, players are captured somewhere in their follow-through.
END OF STROKE
And on the sixth image, this conventional analyzes ends when the entire stroke is completed.