The desktop apps have a built-in updater, so that whenever a new version of the app is released, you'll get the update automatically. When a new version is available, you'll be prompted to install the update and then relaunch the app. Whenever you see this option please click the Install and Relaunch option. If you restart the app in the normal way through quitting, then the update won't be installed.
If you select to ignore the update then you'll be prompted about the update again in the future.
To check the version of the app you're running...
On rare occasions you find it necessary to manually update your app to the latest version. To do this you first need to uninstall the current version of the app.