: Could refer to the quality (e.g., 16:9 aspect ratio) or another attribute of the video.
: This part appears to be a filename or identifier for a video. "10musume" could be a series or brand name, "121314" seems to be a date in the format 12/13/14 (December 13, 2014), "01" might indicate it's the first video in a series or collection, "Azusa Sasaki" is the name of the performer, "MP4" is the file format, and "16" could refer to the video's resolution or another technical specification. : Could refer to the quality (e
: This phrase is Italian for "applause happens." It appears to be an artifact of an automated translation or a specific tag used by an Italian-speaking uploader or forum where the file was cataloged. Availability and Quality : This phrase is Italian for "applause happens