Similar to heh, in that it can be used as a filler for other words, or a neutral acknowledgment of what someone has said. Origin of the word is fuzzy, much like pwned it may have arisen as an error when typing heh. Like heh, the use of this word is difficult to master, and simply allowing it to naturally enter your vernacular is best.
<Wing> Heh at school I found this chick passed out in the hallway.
<NKD> hrhhhhhh
The initials/ nickname of a beautiful and glamorous woman. Exudes intelligence and class at all times. Worshiped and adored by all. A loyal friend and cat lover.
"I have waited my whole life to meet an HRH to carry on my gene pool"