The main types of lens that you will find in most glasses are ‘Single vision‘, ‘Varifocal or Progressive‘ and ‘Bifocal‘ and ‘Occupational‘.
Single Vision lenses
are often known as Distance or Reading glasses and have a single prescription that takes up the entire surface of the lens.
You can find out more about Single Vision Lenses here.
Bifocal lenses
are two lenses of different prescriptions that are bonded together to make a single lens. There is a distinct horizontal line across the lens where the two prescriptions join. They are generally much cheaper than Varifocals.
Progressive Lenses
are also known as Varifocals. They are a technological evolution of Bifocals but instead of being two lenses of different prescriptions bonded together, they are a single lens with the upper part of the lens, the middle of the lens and the lower part of the lens ground to different prescriptions with a steady gradient change between all three areas. They are becoming very popular with people who require more than one type of glasses, but they can be expensive.
You can find out more about Bifocal and Varifocal lenses here.
Occupational lenses
are a type of varifocal that are used for specific tasks. For instance if you are working in an office on a computer all day, you might find that your eyesight is improved if you have a set of glasses that just have a reading prescription on the lower part and intermediate prescription on the upper part but there is no distance vision section.
You can find out more about Occupational lenses here.