Features that require package identity
Some modern Windows experiences require your app to have package identity at runtime (in other words, your app needs to be packaged). Those experiences include certain Windows features, certain Windows Runtime APIs, package extensions, and UWP components.
Universal Windows Platform (UWP) apps receive package identity by default because they can be distributed only via MSIX packages. Other types of Windows apps, including WPF apps, can also be deployed via MSIX packages to obtain package identity. But apps packaged with external location also has package identity. For more info about these terms, see Advantages and disadvantages of packaging your app.
Only packaged apps (including apps packaged with external location) have package identity at runtime. If your app has package identity, then you can use the following features in your app.
Notifications
The Windows App SDK notifications APIs require your app to have package identity.
Integrate with package extensions
If your app needs to integrate with the system (for example, establish firewall rules), then describe those things in the package manifest of your app, and the system will do the rest. For most of these tasks, you won't have to write any code at all. With a bit of XML in the manifest, you can do things such as: start a process when the user logs on; integrate your app into File Explorer; and add your app a list of print targets that appear in other apps.
For more info, see Integrate your desktop app with package extensions.
Get activation info for packaged apps
Starting in Windows 10, version 1809, packaged apps can retrieve certain kinds of activation info during startup. For example, you can get info related to app activation from opening a file, from clicking an interactive toast, or from using a protocol.
For more info, see Get activation info for packaged apps.
Extend with UWP components
Some Windows experiences (for example, a touch-enabled UI page) must run inside of an AppContainer. In general, you should first determine whether you can add your experience by enhancing your existing desktop app with Windows Runtime APIs. If you have to use a UWP component to achieve the experience, then you can add a UWP project to your solution, and use app services to communicate between your desktop app and the UWP component.
For more information, see Extend your desktop app with UWP components.
Distribute
If you package your app in an MSIX package, then it's very easy to distribute it by publishing it the Microsoft Store, or by sideloading it onto systems.
For more info, see Distribute your packaged desktop app.