The Segment Type Box (STYP) is a container in ISO Base Media Format (MPEG-4 Part 12) that provides information about the type of media segments within a file. It's typically used in fragmented MP4 files, where a media file is split into smaller segments for better streaming and management. The STYP box provides information about the type of the media segments, such as audio, video, or text, as well as the version of the codecs used. This information helps decoders understand the format of the segments and decode them correctly.
https://www.w3.org/TR/mse-byte-stream-format-isobmff/#h-iso-media-segments