Not sure if serious. A 12 string has strings in pairs on the guitar so when you play it you get the two strings sounding together. Generally when you see a two necked guitar it is a combination of a 6 string (one neck) and a 12 string (the other neck) You can tell if it is a 12 string by looking at the tuning pegs. If there are 12 of them you are looking at a 12 string.
If you listen to stairway to heaven, Jimmy Page starts the simpler portion of the song on the six string of his double neck guitar and as the sound gets broader he is playing the 12 string.
[video=youtube;9Q7Vr3yQYWQ]https://www.youtube.com/watch?v=9Q7Vr3yQYWQ[/video]
And no, I don't play the guitar so if I got something wrong someone will have to correct me.
Of course this doesn't even touch on acoustic vs. electric.