The only difference between a supermarket and stock market is that, in a super market you buy & sell FMCG, whereas in a stock market, financial securities are transacted.
The above comparision is posted just to understand the bare meaning of stock exchanges. There are so many intermediaries and other institutions who facilitate these transactions.
Stock markets are one of the key indicators of the Performance of an Economy.
When the companies listed in the stock markets are bubbly and tide over a sea of changes, the value of their stocks listed on the exchange undergoes a change.
In a crisis, where the economic conditions are not very favourable, for instance Very high lending rates, Lack of confidence on the company etc., the stock markets are bound to under perform.