Résumé
The definition of descriptional complexity of finite objects suggested by Kolmogorov and other authors in the mid-1960s is now well known. In addition, Kolmogorov pointed out some approaches to a more fine-grained classification of finite objects, such as the resource-bounded complexity (1965), structure function (1974), and the notion of (α,β)-stochasticity (1981). Later it turned out that these approaches are essentially equivalent in that they define the same curve in different coordinates. In this survey, we try to follow the development of these ideas of Kolmogorov as well as similar ideas suggested independently by other authors.