The stock market provides a market for setting prices based on supply and demand

More about the stock market

The stock market provides a market for dealing in listed shares, and for setting prices based on supply and demand.

It is for this reason that prices of equities fluctuate.

Just as in any open market, prices will go up if there are more buyers than sellers and vice versa.

Most of the buying and selling occurs electronically today.

The performance of the stock market is often gauged by the performance of an important index.  An index reflects the performance of a grouping of shares. 

The best known index in the world is the Morgan Stanley Capital Internation (MSCI) Index, which represents the biggest shares in the world based on market capitalization.  When the prices of these shares dip, the index will also go down, and vice versa.

For each country, the main index consists of the biggest shares based on market capitalization.  There are also other sub-indices (financials, industrials, mining, etc.).  Each of these indices represents a certain grouping of shares based on their market capitalisation.