Quote Originally Posted by Ramil
In addition to the bond, the investor has some further upside,
It means that the investor gets additional securities that allow him to profit more from the stock price appreciation.
generally in the form of some warrants which are struck at a premium to the IPO price.
It means that the strike price of the (apparently, call) warrants (usually they are simply privately written options) is set above the IPO price. Meaning that if, say, the IPO is placed at $50, the investor also gets a few warrants with a strike of e.g. $55 (i.e. rights to buy stock at $55), gaining $5 on each if the price appreciates to $60.