What is the difference between monofocal and multifocal lens

I believe you are referring to a monofocal lens compared to a multifocal lens. The monofocal lens has one point of focus which is usually set for your distance vision but you would be blurred for near vision. In many cases, one eye can be set for a distance focus and the other eye for a near focus (so called "monovision") to reduce the need for reading glasses. This type of lens is usually covered by your health insurance. Multifocal lenses are considered "premium lenses" and patients have to pay additional fees both for the lens and for the surgeons to implant the lens. These lenses have both a near and a distance focus out of the same lens (much like bifocal glasses) so the need for reading glasses is reduced and both eyes see both far and near. Their are advantages and potential disadvantages to either type of lens so you need to discuss your options with your surgeon.