CC is the name that is given to UNIX Compiler Command. This is the type of default compiler that you will have when you would like to make sure that your operating system is working properly. GCC is the term given to GNU Compiler Operating System. If you would check, the system that makes use of Linux will normally use CC.
Take note that you need to know exactly which compiler system you should use because there are some differences with the compatibility that you need to use. If you would need to use a full library that makes use of CC, you cannot use GCC in the process, as this will not work at all.