Typical uploads here are Zoom and Teams recordings, OBS screen captures, lecture recordings, and phone footage. All of these carry compressed AAC audio that the model handles well. If a video has several audio tracks (some screen recorders save mic and system audio separately), the first track is used — export with tracks merged if you need both sides of a call.
Anonymous uploads are deleted automatically 24 hours after upload, the video file and the transcript both. With an account the two come apart on purpose: the transcript stays in your library until you delete it, while the video file itself is deleted 72 hours after the transcript finishes, leaving the text. Either way the video is only ever stored to be transcribed; it isn't used for training or shared anywhere.