IPO is the initial public offering of shares.
These are the shares of companies that are listed on public stock exchanges for the first time. This means it's an opportunity to be one of the first to get access to them.

What could be advantage? It's simple. Buying shares of companies at the stage of IPO there is an opportunity to do it much cheaper than in the future will be the price of these shares.
If the interest in the assets of this company will be high, the price of these shares will grow significantly allowing the trader to earn on it.