What IS an "audio file type," and what does that mean in transcription?
Like other computer files, digital audio files have different internal formats and therefore different file extensions depending on how (using what hardware or software) they were recorded.
Some of the audio file types that you may see are .dss, .mp3 and .wav. You will likely see several other audio file types in addition to these.
What this means in transcription is simply that you need to have software that works with a foot pedal that will play whatever type(s) of audio files you need to transcribe.