What is the difference between single-vision and bifocal/progressive lenses?

Single vision lenses refer to lens that have only one use, to see objects in the distance,  to see intermediate like computer or phone, or to see near for reading (reading glasses), while bifocals/progressives are a type of prescription eyeglasses that can be used to correct both near and farsightedness. This means you can see your whole field of vision without switching between multiple pairs of glasses.