In the book we discuss theoretical-methodology basis of domain functioning of the investment; investment domain is stated to be the consisting part of economic system;first time in the Georgian economical mind investments are considered to be economical category; investments are represented as a form and mofifier of finances, together with a credit. There are modern conceptions and development models of the investments, their macro- and micro- econimical aspects in the book; a model of investment behavior of the enterprise is represented separately.