“In layman’s terms, ergonomics is the science of designing a workplace (or job, system or product) so that it best fits the capabilities and limitations of the humans who work there (or use the product or system). Essentially it is about creating a better, safer, more satisfying workplace for those who work there, which, in turn leads to improved productivity and ultimately, enhanced business performance.
Perhaps this story about Procrustes from Greek mythology may help you understand ergonomics better. Procrustes was a robber who had a nasty habit of tying any unfortunate traveller who came across his path to an iron bed. If they were taller than the bed, he would chop off their legs to make them fit. If they were shorter, he stretched them until they fitted the bed. If Procrustes had understood ergonomics, he would have made the bed (workplace) fit the person (worker), rather than the person fit the bed.