Mixdown : Export Audio Mix Options : File Type
 
File Type
The File Type selector lets you select the file type for the exported file.
WAV (Broadcast .WAV Format)
This format is supported on Windows and Mac. To use a WAV file in Pro Tools | First, you can drag and drop from a Workspace browser, Windows Explorer or Mac Finder, or a folder, or you can use the Import Audio command. Files in this format do not have to be converted to be used in Pro Tools | First.
AIFF (Audio Interchange File Format)
This format is supported on Windows and Mac. To use an AIFF file in Pro Tools First, you can drag and drop from a Workspace browser, Windows Explorer or Mac Finder, or you can use the Import Audio command. Files in this format will be converted to WAV imported into Pro Tools | First.