GMP IPO or grey market premium of an IPO is the difference between the IPO price and the price  at which its trading in an Unregulated or secondary market before its listing on the regulated Exchanges. GMP of IPO or Grey Market Premium helps to determine the market sentiment and expectation regarding the future listing price.

GMO of an IPO represents the premium or discount at which a stock is trading in the Grey Market. A Postive GMP indicates that the stock is in demand and investors are willing to pay more than the IPO price, Stocks trading at a premium in Grey market  perform better after listing on Regulated exchange

A negative GMP indicates lack of interest in the  stock and investor are not interested to pay premium prices from its issue price