both.. Jpeg, Gif are image files... MP3, Wave, etc (plus 3 to 4 others).. are Music Files and Mpeg is Videos.. There are actually a couple of other Video format extension that will work with all portable players except Ipod. But, I can not for the life of me think of them at this time.
All these files can be read by a Window base PC plus devices such as MP3 and MP4 players (portable Music and Video Devices)...And these file can be easily transfer from one device to another via USB, Firewire, or WiFi (wireless Internet)
