J.
Coatings on lenses are designed to minimise reflection and maximise transmission of light.
In binos you want fully multi-coated (FMC) optics, if you can at all afford it. You can get good FMC binos from
www.aoe.com.au starting at around $100.
coated = at least one air-glass surface has at least a single layer of coating
fully coated = all air-glass surfaces have at least a single layer of coating
multi-coated (MC) = at least one air-glass surface has at least multiple layers of coating
FMC = ... well you get the idea.
Multi-coatings work on multiple colours, single layer coatings are tuned to just one colour. The best multi-coatings work at right across the visible spectrum.
In practice FMC will give you higher contrast, less light scatter and less reflections and glare off bright objects.