Those three simple buttons dangling on the left side your Apple headphones hide a decent amount of usefulness. Play/pause, next track, answer call, talk to Siri, etc.
Many of you who have been already using your headphone with your Apple device might already be knowing many or most of these functions. However, I’ll try to include all possible functions of the headphone for the benefit of those who don’t know it.
Don't forget that most of these controls also work when plugged into your Mac's headphone jack, too. Oh, and many third party headphones, like my beloved Phiaton Chord MS 530's, include these same buttons and work in the same way.
(via Minimal Mac)
Update: Jordan Merrick has a great followup piece and turns this topic up to 11. Read it.