The phrase refers to tools and services that facilitate the extraction of audio content, specifically in the MP3 format, from video content hosted on YouTube. These tools allow users to obtain an audio file from a video, enabling them to listen to the audio portion without needing to view the visual component. For example, a user might utilize one of these services to create an MP3 file of a song found on YouTube.
The utility of these services stems from the desire to access audio content in a portable, easily manageable format. This allows for offline listening, reduced data consumption compared to video streaming, and compatibility with a wider range of devices. Historically, the demand for such functionality arose concurrently with the popularization of both YouTube as a primary source of media and the MP3 format as a dominant standard for digital audio. This demand has spurred the development of numerous websites and software applications offering this specific functionality.