The term big data is a new, shaping up concept. In this paper, the authors propose a three-faceted explanation of the term, by distinguishing three basic aspects of big data: technological (including the opportunities offered by IT and modern analytical methods), business (including a variety of applications of the concept) and social (focusing on the consequences of its implementation). The authors also indicate some other aspects, e.g. legal, which can be used to extend the classification. The social aspect, mainly concerning the risks associated with the mass processing of personal data and privacy, is usually overlooked when trying to define the concept.