This abbreviation is standard for "Season 1." In the world of digital piracy and archiving, organization is key. Television shows are rarely released as single monolithic files. Instead, they are broken down into seasons and episodes. The Head was marketed as a limited series, but the open-ended nature of the finale left room for potential continuation. For the archivist, labeling this "S01" implies a complete collection of the initial run of episodes, likely bundled into a single torrent or directory.
The Anatomy of a Digital Release: Understanding "The Head 2020 S01 WEBRip x265-ION265" The Head 2020 S01 WEBRip x265-ION265