The phrase refers to a type of online service or software designed to extract the audio track from video content hosted on YouTube and convert it into the MP3 audio format. For instance, a user could employ such a utility to download a song found on YouTube as an MP3 file, enabling offline listening.
These conversion tools provide a convenient method for individuals to access audio content from YouTube videos for personal use. They became increasingly popular due to their ease of access and the vast library of music and audio recordings available on the video-sharing platform. Historically, their rise coincided with the widespread adoption of MP3 players and portable audio devices, creating a demand for downloadable audio files.