Open Interest

satari, this site is good for basics on open interest
http://openin.blogspot.com/

Open Interest (OI) is the total no. of contracts that are "live" and outstanding for a particular underlying (for futures) and for particular strikes (for options).

Examples:

"The Feb Nifty OI is 15 lakhs" means that at that instant a total of 15 lakhs of outstanding contracts (30,000 lots of lot size 50 each) are outstanding for Feb expiry.

"The Feb Nifty OI increased by 2 lakhs" means that 2 lakhs of new contracts were created in futures expiring in Feb. If this is accompanied by an increase in premium of futures over the spot nifty price(say, increase from 5 pts. premium to 20 pts. premium), then it normally means that most of the additional 2 lakhs of new contracts were long positions.

OPEN INT. and PRICE increasing---STRONG MARKET(new buyers),O.I. increasing but PRICE decreasing-----SHORT SELLER.Both O.I. and PRICE decreasing---STRONG MARKET,O.I.decreasing but PRICE increasing----SHORT COVERING

Try

Options Outlook

When in doubt for any term, always consult investopedia

http://www.investopedia.com/terms/o/openinterest.asp