All right, I got this laptop a few months ago and have always just used the middle jack on the side. The one closest to the other ports is said to be headphones and on the opposite side of the middle jack is a mic/input.
I always used the middle because it was simple to remember, but recently I had a bud over and we both had headphones connected to my computer, but his didn't have audio out of that jack. and when I disconnected mine but left his in, it played through the internal speakers. Acting like the port didn't exist!
Now I've been through the settings and it knows it's there. It just doesn't work.
I thought it was strange and just used the internals for that day. But it would be nice to use both of those for the future. Like if I have my audio equipment hooked up I could also have some monitor headphones in the computer too.
It isn't a huge deal, but it is a bit bothersome.
I've heard that they work indepentantly, with one grounded differently.