China has a very rigid time schedule, that application are published 18-months after filing date. Anyone who cares to know, can go to the web site http://www.sipo.gov.cn to search for it. That means the invention as described in the application becomes publicly available. Patent applicant may consider to request for examination (if not already done so). Applicant can request for examination within 3 years after filing, failing which, it lapses.
Applicant can withdraw the patent application before publication, then it would not be available to the public, the application and the knowledge related to the invention will remain confidential. Once it is published, then it is no longer confidential information, as the original patent application was intended for 'skilled person of the trade' to understand and to build the embodiment according to what was disclosed in the application. So filing a patent application without going through examination like disclosing your way of building a new invention.
Having said that, there are clients who just want to file an application in China and do not want to spend time and money to go through the patent examination process. There are different commercial considerations for doing this. One being that you have three years' time to claim that you have one 'patent-pending' for the cost of the filing. If the invention is not commercial viable after testing the market for 18-months, applicant can just abandon the patent application.