My appologies that the following may be mildly offensive or insulting but I hope it is insightful.
If you'd followed the link, and scrolled around you'd have found an explanation of code groups, and several links to more information and articles discussing them. If you hope to get a job you're going to have to learn how to do this kind of research. With the enormous amount of technology we are surrounded with, it's rediculous to think that someone can know all there is about even one technology to do his/her job. What's more important is that you recognize that you *don't* know something but can figure out how to find the answer or learn enough about it to understand and implement it. I didn't know a thing about code groups, but in less time than it took me to type this reply I found several articles about them.