Dwell is a Traditional Motion-Law.
Dwell is a 'Polynomial' Motion-Law.
Segment-Editor or the Blend-Point Editor you ...
... CAN specify the:
Position usually flows from the Previous-Segment.
... CANNOT specify the:
A Dwell keeps the position at a constant value.
Use the Dwell when you want a stationary Motion-Part.
Dwell is used far too frequently. The longer the Dwell, the shorter the other segments, and hence their peak accelerations increase and become shorter, which increases their harmonic and frequency content.