Flow of funds in the financial markets:

In a modern economy, income is partly spent for consumption and partly saved, and much of the saving is channeled into investment via the financial system.  An efficient financial system assures the flow of such loanable funds into their most desired uses.

These institutions and markets provide borrowers with funds needed now, while at the same providing lenders with a variety of financial assets with varying degrees of safety, liquidity and yield.

Saving and investments are 'flow' concepts as opposed to stock concepts. Investment is the process of capital formation. The existing stock of capital depreciates overtime as it is used in producing consumer goods or other investment goods, so the net  investment is the net addition to the stock of capital occurring over a period of time.  These additions to the stock of capital are "real" investment. 

Saving is a residual concept.  Ti is that part of the output of or economy that is not consumed.  Output is produced over a period of time; post of that output is consumed, another part is saved is added to the stock of wealth and presumably is available for
use in future.  Thus, by definition, saving is identical to "real investment that occurs over a period of time.

Saving and Investment and National Income Accounts:

Relationship between saving and investment and national income accounts are now presented in this subsection in a simplified form. we may view expenditure for final output as consumer expenditures, government spending, gross investment spending, and net spending by foreigners for exports. The same total amount may be viewed as income received by those who receive wages, rent, interest and profits. Income may be used for consumption spending or may be used. 

Saving may be used for direct investment, or it may be used for financial investment, in the purchase of financial assets. Financial investment may go directly into loans and investments or may be channeled through financial intermediaries such as banks, savings and loan associations, life insurance companies and others.  Funds received by such institutions may be channeled into business loans and investments, investments in government securities, or consumer loans.  Amounts loaned to consumers may be used for them for consumption.  Similarly, amounts lent to government provide funds for the government to use for current spending.