This emoticon
literally means "
heart" since that is what it looks when viewed sideways. In IM language though, it's a less serious way of saying somebody you "love" them, or at least "care for" them. Even if you do really "love" somebody, you
don't want to say it every minute and every day -- it gets old and may even scare him or her. So, use "<3" for normal every day conversations, reserving "love" during the times you really want the other to know you mean it.