Forces are best described as pushes or a pulls. When you weigh yourself on a bathroom scales your body is forcing the scales down toward the center of the earth. The amount of force exerted by your body is indicated in pounds. Pressure - force per unit area. Atmospheric pressure is 14.5 pounds per square inch.
Pressure is exerted by liquids and gases and is equal in all directions.
Stress - the term we use to denote force per unit area within a solid such as rock. A tensional stress stretches rocks, compressional stress squeezes them, while a shear stress causes slippage or translation. Differential Stress - solids such as rocks can support different magnitudes of stress in different directions. The difference between the largest and smallest stress is called differential stress . The largest and smallest stress always act at right angles.