The article describes various aspects of symbolic mediation and is aimed at showing its specificity. The author views a situation of uncertainty as a structural element of a symbol and introduces the notion of a symbol being a special tool for orientation in such situations. On the one hand, a symbol is contrasted to a sign, and on the other, is regarded as a transitional form in the process of its mastering. Author pays special attention to understanding the role of symbol in connection with understanding of play and its role in child's development. Emotional and cognitive functions of symbol are defined and illustrated by examples