In chat-speak and texting, the "less than" sign followed immedately by a 3 creates a heart set on its side: <3 I suspect that your friend accidentally typed in two 3s instead of one. There are a number of "chat dictionaries" online that offer extensive lists of clever things you can do in IM or while texting.
It look like a heart's sideways,more three's(<3333333) refers to more hearts like the less than symbol shows the end portion of the heart and the 3 shows the top portion of the heart. ,if the number is next to your name then the person loves you a lot. In other meaning it is an emoticon basically looks like a smile.