I'm new with Mac os and have few questions about the groups(I guess the question applies to unix too).I know what Primary and Secondary groups are, but as I was reading the articles about the difference between those two, I came across with this terminology that I could not understand. As I understand default groups are ones that are created on fresh install, but what is the difference between default and supplementary groups? Is supplementary group same as secondary groups? If not how can I differentiate that? thanks.  
suplementary vs default
osx;group