You can use the mic button on your Apple iPhone headset to perform commands like putting calls on hold and skipping songs while listening to music. Here’s a list on how to do it.
Answer an incoming call:
End the current call:
Decline an incoming call:
Press and hold for two seconds, then release. Two beeps confirm you declined the call after you release the button.
Switch to an incoming or on-hold call:
Click once. Click again to switch back to the first call.
Switch to an incoming or on-hold call and end current call:
Press and hold for about two seconds, then let go. Two beeps confirm call has been ended after you release the button.
Pause a song or video:
Click the mic button once. Click again to resume playback.
Skip to next song:
Click twice quickly.
Source: iPhone User Guide
Can I use third-party buttoned headphones that are not Apple brand to issue commands to my device?
Yes. The 1 and 3 button headsets should be compatible with the iPhone.