As somebody who reads a lot of “economics for laymen” books, I find some of the esoteric microeconomics theory or hardcore mathematics boring. Occasionally there is an obscure topic worth learning: labour demand elasticity is such a topic.
The price of labour often affects the demand for it. If wages fall, we might expect higher demand as employers take advantage of the inexpensive human capital by hiring more people. The relationship between the two is “labour’s elasticity of demand”, and it’s the answer to the question, “by how much will employment increase if workers are X% cheaper?”