Drying shrinkage
The gradual volume reduction that occurs as concrete loses moisture over months. It is the fundamental reason concrete cracks and why control joints exist.
What does drying shrinkage mean?
Every slab shrinks, and because it is restrained by friction against the subgrade and by anything it is attached to, that shrinkage produces tension the concrete cannot resist. More water and more paste mean more shrinkage, which is why wet mixes crack more. The practical response is not to prevent shrinkage but to decide where the cracks will go.
In practice
A homeowner asking how to get a driveway that never cracks is asking for something the material cannot do; the real goal is cracks that follow the joints.