No classificatory system is inherently 'better' than another. The only criterion for the success of a classification system is its utility. Because different people have different needs, what 'works' for one individual may not for another. But this lack of universality doesn't dissuade each of us from working out a system that is right for our purposes. Try as we might, we cannot seem to resist grouping, organizing, and classifying everything we come across.
Taxonomy is the scientific art of classifying living things.
According to Linnaeus' system, each species is given a unique, two-part name called a binomen . Each binomen consists of a genus and species epithet. The species is the basic unit of classification and the only 'natural' one. All other taxa are arbitrary, and therefore subject to changes due to new data or interpretations. It is therefore surprising that experts differ in their definition of what, exactly, a species is.