Original: The second -, third -, and fifth-generation iPod Shuffle uses a single 3.5 mm jack which acts as both a headphone jack and a data port for the dock. The dock connector also allowed the iPod to connect to accessories, which often supplement the iPod's music, video, and photo playback.
Simplified: Another type of iPod, called the iPod shuffle, is very small, and it uses flash memory, like the iPod nano but it has no screen.