Are you and your girlfriend/boyfriend compatible? Are you destined to spend an eternity together? Who knows? This sure as hell won't tell you that, but it is good for a giggle to see how you measure up.
Okay, stick your name in one side, and your girlfriend/wife/mistress/object of desire/woman you will never have in the other side and hit "Calculate". Then laugh at the result and book some time with a Shrink to discover why you actually just bothered to do it.