Correct audio jack.

So I hope this doesn't come off as a dumb question but which of the two inputs the headphone or headset should I use to hook up my external speakers? Or does it even matter? For some reason I wasn't getting stereo sound out of my external speakers today and I'm assuming it was because I hooked up to the micro phone port by accident. Which I didn't think it really mattered since it prompts you choices when it detects an outside input. For some reason when I put my PC to sleep and turned it back on the sound went to non-stero. ( no subwoofer or mid-range speakers ) thought's