When a bar is pulled in tension, it has to get longer. The tensile modulus is used to calculate how much longer it will get when a certain load is applied to it. Units are normally millions of pounds per square inch. (10 psi) - Giga Pascals (gPa). Higher numbers indicate materials which will not elongate as much as others when they are being compared under equal tensile loading conditions.
A measure of stiffness, i.e., how much a material will bend, stretch or compress under a given load and still come back to its original size and shape. When measured in compression, it may be referred to as "compressive modulus". The same thing holds true for tension and flexural moduli. The modulus will be given in terms of pounds per inch and may be expressed exponentially, e.g. 8.8 x 104, which merely means 88,000 psi.