What is an RxD lens?

Could you please elaborate on what an RxD lens is? I'm curious to know if it's a specific type of optical lens used for corrective vision purposes, or if it serves a different function altogether. Additionally, I'm interested in understanding the science behind RxD lenses and how they work to improve or address various visual impairments. Can you provide more insight into their design, purpose, and potential benefits for those who may require them?