Pressure

Pressure is defined as the Force per unit of area.

Its unit is actually a which is also called the Pascal.

As an egg hits the ground, only a small area of the egg actually comes in contact with the floor at first.  This means that the force applied by the floor to stop the egg acts on a small surface area.  This results in a huge pressure which typically cracks the egg.

Since the egg is a curved surface only the point tangent to the floor touches the ground.  This very small area is very similar to looking at the egg falling onto the point of a nail.  Either way the force acts on a very small area.   The nail also leads to a huge, shell busting pressure.

If the egg is placed in a contoured holder, the force on the egg is spread out over a larger area which results in a lower pressure on the egg.  If the pressure is small enough, the egg will not break.