Explain award on CV?
In my experience it is usual (and useful) to explain awards in the CV, even for well known awards (well, maybe not the Nobel prize; but otherwise not assuming that everyone knows your award and not assume that they should just google it seems quite polite.)

Do not use the self-description ("outstanding achievements bla bla") but the set of eligible candidates and the frequency and number of awards (e.g.: "One prize each year awarded by the Belgian Academy of Sciences to a biologist working in Belgium.") 

As Roland commented: If the name of the award does not imply it, or if the award is not in some obvious way for "the overall best among the eligible candidates", then add what the award is for.

So I would write


The golden srcub (for the cleanest laboratory, one prize each year awarded by the Belgian Academy of Sciences to a biologist working in Belgium.)


But just 


Prize of the Belgian Society of Biology (awarded biannually to a Belgian biologist under the age of 30.)


In that case I personally would not say "to the best Belgian biologist under the age.."; it seems clear that this is implicitly the aim of the prize, and claiming to be "best" sounds pompous.

Btw, I just saw that the question seems to be answered here already.