Yes, this is an old scam, what they're trying to do is to scare you into buying/registering your domain name on other TLDs. You probably own the .com and they want you to register the .cc, the .tk, ...

Chinese internet keywords are a short form words of your url for exemple for http://www.mysite.org you can register mysite, anyone typing mysite in the address bar of their internet browser will be redirected to http://www.mysite.org but this only work in China and only on certain supported internet browsers.

I advise against dealing with them, if you wish to register chinese domain names or internet keywords you can easily register them through a reputable registrar.