The purpose of this paper is to analyse existing theoretical and practical approaches to the explanation of the essence of business clusters. This study observes the nature of clusters, as well as inspects dynamic changes in the perception of a cluster as an agglomeration. The research is based on a literature review, within the scope of which theoretical approaches are divided into four categories, namely the British, Italian, American and Scandinavian visions. Not only does the paper contain detailed examinations of the approaches, but it also reveals an evaluation of each approach from the position of nine measurement criteria that are proposed within a comparative analysis. The choice of implemented criteria is justified by their significance for the description of clusters. Apart from that, the study highlights distinguishing features of all approaches.