The files offered on our Free Downloads page are either MP3 audio files or zipped files. The monthly events for example are always MP3 files that don't require unzipping. Other downloads such as DAISY files do. There are several, if not hundreds of files within a DAISY book, which is why they are always zipped.
If you view a download's details you'll always see file names including information on that specific file's format. Two examples are "AWorldOfChromebooksWithQuestions.mp3", and "BrailleNoteTouchPlusDAISYAudioTutorial.zip."