The best information I could find so far on the subject is Wikipedia:
Unlike the Web, where the underlying technology of HTTP and URLs allow
for deep linking by default, enabling deep linking on mobile apps
requires these apps be configured to properly handle a uniform
resource identifier (URI). Just like a URL is an address for a
website, a URI is the address for an app on a mobile device. Examples
of URIs that launch a mobile app:
twitter://
is the iOS URI to launch Twitter’s mobile app
YouTube://
is
the iOS URI to launch YouTube’s mobile app
The format of the URI used
to trigger or deep link an app is often different depending on the
mobile operating system. Android devices work through intents,
BlackBerry 10 devices works through BB10's invocation framework,
Firefox OS devices works through Web Activities, iOS devices works
through the openUrl
application method, and Windows Phone 8 devices
works through the UriMapper class.
fb://profile/33138223345
is an example of a mobile deep link. The URI
contains all the information needed to launch directly into a
particular location within an app, in this case the profile with id
'33138223345', i.e. the Wikipedia page, within the Facebook app,
instead of simply launching the Facebook app fb://
. eBay's apps
demonstrate the use of different schemes by platform.
eBay://launch?itm=360703170135
is the URI that deep links into eBay’s
iOS app while eBay://item/view?id=360703170135
links into eBay’s
Android app
Basically the URL matching starts at the OS level.
iOS will use the settings in your apps plist file for a whole bunch of other things outside the app. One of them being the deep linking.
You declare your URL scheme in the plist, and whenever the OS encounters a URL matching this scheme (usually when user taps a button or link), it will open your app and pass the URL information on. It's then your responsibility to determine what to do with this information.
Does it jump into a profile page? A particular product? That's all left up to you.