Nothing, idiots. You all mean Heartagram, made by HIM, not H.I.M.
a Heartagram is a symbol made up by the band HIM which is a mix between a pentagram (Notice pentAgram, not pentOgram) and a heart.
The symbol was then stolen by the second biggest douche (the first being John Edwards) in the universe, Bam Margera.
It's not Heartogram you newb. Even HIM's website is www.heartagram.com