How does computer differentiate if I plug headphones or speakers?

i was wondering how PC know which speaker I plugged in? When I plug in standard pc speaker, my pc says that speaker is connected. If I plug in headphones, PC says that headphones are connected. Does speakers/headphones has some kind of memory to store information, or what? I mean, speaker device can't send digital information throught 3.5mm jack (right?), so there must be some kind of analog information to send (beside the sound itslef). I am not familiar with electronics so I am sorry if question is stupid. Thank you.

Question by stfnsn on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.