Droop measures how far down the car’s suspension arms are able to travel, or specifically the difference between the car’s natural ride height and its maximum ride height when the wheels just lose contact with the ground. On some setup sheets, it is measured as the distance between the center of the shock’s two mounting screws.
Droop is usually changed via internal shock limiters or on some cars via specific droop/downtravel/downstop limiters.
Droop allows or limits the weight transfer from one side of the car to the other.
Less front droop
More front droop
Less rear droop
More rear droop
Stroke measures the distance between full compression of the shock and full extension. Stroke can be changed via internal limiters (downtravel) or external limiters (uptravel.)
Changes to the car’s ride height will also change its droop if no other adjustments are made.