as index is a value to compare with why do we have different indice , correct me if i am wrong?
Dinesh,
The varying indices measure different things. For example, the Dow has 3 different indices, one for industrials, one for transports, and one for utilities.
S&P also has several, the S&P 500, the S&P 100, and their midcap (smaller companies that what’s in the 100.
Here’s a link to several: http://quotes.nasdaq.com/aspx/marketindices.aspx
Wikipedia has a long explanation of why there are so many:
http://en.wikipedia.org/wiki/Stock_market_index
Hope that helps.