An initial public offering (IPO) is the first time a company issues shares to public investors and is listed on a stock exchange (such as the Hong Kong Stock Exchange) for trading. Investors can subscribe for the shares issued during the IPO.
If an application is successful, the shares can be purchased at the final issue price on the day of listing. This is called an IPO subscription, which is commonly referred to as a new share subscription.
Official introduction to the Hong Kong Stock Exchange.