The earbuds included with the 3rd generation iPod have a remote microphone and controls for:
- Volume (+/-)
- Pause/Play (press the depressed area between + and - once)
- Next Track (press that depressed area twice)
- Previous Track (press that depressed area thrice)
- Voice Control (press and hold that depressed area)
The Next/Previous Track options allow you to move between consecutive (previously downloaded) episodes of a podcast series.
Voice Control for podcasts appears to have no particular utility. Most of the options that glide by on the screen are for music (e.g., play album, shuffle, etc.), although iOS devices with a camera can invoke FaceTime as well.
I recently upgraded to a 4th generation iPod (a blog entry is forthcoming). Its earbuds lack the remote microphone and controls (the lack of a 3rd white band on the jack is an indicator of this); those are available on the iPod itself, although they are less convenient to use. This is the first iPod to have a built-in microphone. Volume can be controlled by the iPod's physical volume buttons. iOS 5 added the ability to press the Home button twice to access Pause/Play, Next track and Previous Track buttons on the touchscreen.
The model of Skullcandy Smokin' Buds earbuds that came with my 4th generation iPod duplicate the functionality of 3rd generation iPod earbuds, except for Volume.