The phrase refers to the acquisition of a modified version of the YouTube application, typically identified by a blue-themed interface, in the form of an Android Package Kit (APK) file. This method bypasses the official Google Play Store for installation. An example would be searching for a specific version of the application online and downloading the file directly to an Android device.
Such applications often promise enhanced functionality beyond the standard YouTube application. This may include ad-free viewing, background playback, or access to features not yet officially released. Historically, these modifications arose due to user desire for functionalities not offered by the official application or restrictions imposed by device manufacturers or regional content policies.