Here is a coated version of Super Ikonta B. The coating is a thin layer of metal covering the glass surface. It can be multicoated going up to several layers (like 7, I was told). It was invented by Zeiss (Zeiss Ikon produced cameras and Zeiss is the optical concern). It might be strange to think of metal covering the glass and rendering it more transparent but it is not so hard to understand. To start, it must be said that it is a very thin layer going to atoms dimension. It is a vapor of several metals that is deposited over. Second everyone of us experienced already to throw flat stones over a calm lake water surface. What happens ? Stones are bounced back when trying to "perforate" the water surface. Light does the same when trying to penetrate the glass. Like the stone it is harder when the direction gets more parallel to the surface. Now imagine that if we could have over the water some layers softer that water to make the transition smoother: the bouncing effect would be reduced. Imagine we could have some foam for instance. Well, to conclude, the metal layer does what the foam would do in the stone air/water transition. To light, the metal layer is softer than glass and has an effect of reducing the bouncing effect.
Bottom line is that the lens looks more transparent when we look at it because there is less light being reflected to our eyes. More light penetrates the optical assembly so we gain in actual f stops. Depending on the lens construction it can be a dramatic increase. Less light gets lost inside the optical assembly, so less uncontrolled light reaches the film fogging it. Normally pictures are sharper with coated lenses. Modern zoom lenses with 15 elements would be impossible without coating. Old Tessars, with 4 elements in 3 groups the coating effect is not that visible in not so contrasty situations.
To identify whether or not a lens is coated it is enough to see if there is some colour on it. Normally there is a light deviation to blue or yellow. That will not tell you whether is a single or multicoated lens and neither if the inner elements are coated or not.

If you want to know more about Zeiss history go to: Zeiss Historica Society
For camera profiles: Camera Quest