: This likely stands for Full High Definition, indicating the video quality is high definition, possibly 1080p or higher.
If you found this file on a public forum or a peer-to-peer sharing site:
Inside that folder, store:
: This could refer to a specific category, series, or brand of content. Without more context, it's hard to say exactly what "SONE" refers to, but it might be related to a production company, a character, or a thematic series.