First of all, what is rebar? Rebar is fabricated steel rods used for reinforcement in concrete.
Rebar is important to install in concrete slabs, like driveways and patios, because it keeps the slab sections even and held together tightly. Rebar prevents the big, wide cracks and this is why:
Concrete has a very high compression strength meaning that if you take a piece of concrete and try to crush it, you will need to exert an extreme amount of force, about 4000 to 5000 pounds per square inch, to break it. On the other hand, concrete has a very low tensile strength. If you take that same piece of concrete and try to pull it apart, it will break rather easily. To counter this problem, rebar is embedded in the concrete. Rebar has a very high tensile strength.
We have all seen concrete that is un-even and separated, especially in the winter. This is because, here in Minnesota, the ground freezes and heaves which pushes up un-evenly on concrete slabs. If those un-even concrete slabs would have had rebar embedded in them, the rebar, being high in tensile strength, would not have allowed the concrete sections to separate and move individually.
Rebar is a must for the structural integrity and longevity of all exterior concrete slabs.