The link to the facebook application starts with fb: // (according to this site ) for the iPhone. Therefore, theoretically, clicking on the link starting with fb: // will launch the facebook application.
The problem is that the web browser application (Safari or some custom application) decides how to handle this link, and will not necessarily try to open another application if it is not programmed for this. If you plan to place this on a web page, for example, and go to it from your iPhone, there is no guarantee that it will work. It is better not to rely on two links.
Not sure if the same is true for Android.
source share