it means you are their "everything" and they love you very much.
It means that you are very important to that person beyond the measures of the world.
When I tell a special someone "you mean the world to me", it means that that person is one of the most important people in my life, that I care for that person more than anyone else, that I love that person unconditionally, that I appreciate that person in any way possible for one person to appreciate another.
pretty obvious someone is making it clear they care or love you and you matter more than just someone they can take or leave without it making any difference. Interesting question:)
probably I'm horny :P
DONT LISSON TO CYNENT HES A LIER IT MEEN YOU GOT A HUG BADONKADONK. LOL<br />
IT MEANS YOU'RE UGLY, AND THEY WANT SOME
"I love you, but I'm not in love with you." They can tell their mom she means the world to them.