In YouTube, a playback ID is a unique identifier for a specific video. It is used to identify the video when it is played back or accessed on the YouTube platform. The playback ID is a string of characters assigned to a video when uploaded to YouTube and cannot be changed. It is used to identify the video in various contexts, such as when it is embedded on a website or accessed through the YouTube API. The ID remains the same even if you change the video title. If you want to note down the ID, look at the string of characters that appears after the "v=" parameter in the URL.