Stocks relate to a point of time.
Stocks do not have time dimension.
Stocks are affected by flows, e.g., the more is the saving, and the more is the stock of capital.
Some stocks have related flows such as money supply and change in money supply.
Flows relate to a period of time.
Flows have a time dimensions.
Flows are affected by stocks.
Some flows have related stocks, such as flow of water and quantity of water in a tank.