Coated Lense Binoculars; information 

By using Coated Lense Binoculars the coating of the lense reduces the loss of light by reflections of the lense. A binocular with a good coating has a sharper clarity than one with the same magnification without coatings. This is particularly important when observing the night sky with a binocular. You want the biggest possible amount of light to reach your eyes and not to reflected back into space from the objectives.
Most modern lenses have antireflection optical coatings on at least one of the air-to-glass surfaces. Very good models will have all glass surfaces coated with multiple layers.

The most used and least expensive coating is a single- layer of magnesium fluoride (MgF), but there are also modern broadband multicoatings. Basically you can divide the binoculars in about four levels of coatings.   

C : Coated, with a single-layer MgF coating on some of the optical surfaces.

FC : Fully Coated, all air-to-glass surfaces have a single-layer MgF coating.

MC :  Multicoated lenses, multi-layer coatings applied on some surfaces.

Recently "ruby" coatings binoculars are a hype. These intend to reduce the glare in bright light and improve the contrast between brown and green objects. Avoid these if you buy a binocular for astronomical use. Your vision quality will go down.