Hynix is a company that makes RAM. Google it, it's not that hard.
Here's a
link for you though.
What is it doing in your RAM slot? You ordered a 512MB stick of RAM from Apple, and that is what they gave you. What's the concern? Other people have reported getting Hynix RAM, too. And, you should be happy about it too, as people have reported success in getting a 128 bit bus when pairing a Crucial chip with their Hynix chip. Unlike what I got when pairing a Crucial/Micron chip with the Micron chip I got from Apple. Go figure...
Also, why the
double post?