The phrase points to a specific version of the YouTube application (version 19.16.39) potentially sourced from a third-party repository known as APKMirror. APKMirror is a website that offers APK files for Android applications, allowing users to download and install app versions that may not be available through the official Google Play Store. This might include older versions or versions tailored for specific devices.
Accessing application versions through alternative sources like APKMirror can be useful for users who require a particular version due to device compatibility issues, feature preferences, or to bypass geographical restrictions or staged rollouts of updates. Historically, such repositories have provided access to software iterations removed from official distribution channels or those not yet officially released.