Gross Investment, Net Investment and Depreciation

Firstly, what is Investment?
Investment refers to the process of capital formation where additions are made to the capital stock of the economy. When a building or a plant and machinery is purchased, an investment is made.
Gross Investment refers to total addition made to the capital stock (in a given period) of an economy. It includes the expenditure on new fixed assets as well as unsold assets during the year.
Net Investment refers to the actual addition that is made to the capital stock (in a given period) of an economy.