An aux cord is a cable most people use to play music off of a device. You will usually find people using these in their car and the aux cord jokes are usually about that. You will find jokes about things like cars blowing up because the mixed tape that was being played was so hot or pushing someone out of a moving vehicle because someone used the aux cord to play whack music.
As most people can attest to not everyone likes the same type of music especially when on road trips or even short trips to the store. You will find jokes in this section about those situations as well. Things like when you play your own music that you created yourself and think its awesome but your friends crack so many jokes and laugh at your music so hard you just sit there and cry.