Elasticity of subsitution is a measure of the curvature of an isoquant1 and can provide us information regarding the nature of the production functions we are dealing with. this is visualized in Advanced Microeconomic Theory by Geoffrey A. Jehle (Author), Philip J. Reny (page 130 in the book) as:
However I wonder, isn't this information regarding the curvature of a isoquant given by the production function? what novel information does the calculation of elasticity of substitution provide us with?
1. I'm aware that elasticity of substitution can also be applied to consumer theory, just that its dominant in producer theory.