Well, to me it's a day to celebrate the person you love. To show them you love them still if you don't do it often. Or it can be a day to show that person youv'e been crushing on that you would like to get to know them.
It doesn't. Like other holidays, it is what you make of it. The ads are all "hearts and flowers" because the companies want you to buy stuff. But they ALWAYS want you to buy stuff; Valentine's Day just gives them a name for it. Do it the way you want to.