The economical essence of investments in analyzed on the basis of special literature studying. Different definitions of investment are presented and their main distinction between this economical term and others terms that have similar meaning. A large classification of investment is presented depending on lot of factors, such as: the investment medium; investment period; the pattern of ownership; the forms of participation in investment; the investment territory; the methods of accounting and others. The meaning of investment is argued for social-economic development of countries and the factors, such as economical growth of enterprises, the employment of the able-bodied population, the rational recourse using, the growth income of national budget and large opportunities of development for enterprises, population and the state. The multiplier effect is examined in this article, that means quantitative and qualitative change of financial flows in economy. The investment creates some spheres, such as: the sphere of capital construction; the sphere of innovations; the sphere of financial circulation and the sphere of realization of propriety rights with application hypothecation right.