Interesting Beetle classified ad

I just stumbled across this ad today.

1991 VOLKSWAGEN BEETLE, sedan, 76,000 kilometers, hot green paint, 17 inch wheels, $2500 audio system, Mexican title, $6,000; (313)894-7113 after 5pm DETROIT #, Phone 3138947113(313) 894-7113

I'm waiting until 5 and I am going to call. I am not interested in buying it, but I am curious how this whole "Mexican Title" thing works.