GCC (upper case) refers to the GNU Compiler Collection. This is an open source compiler suite which include compilers for C, C++, Objective C, Fortran, Ada, Go and Java. gcc (lower case) is the C compiler in the GNU Compiler Collection. Historically GCC and gcc have been used interchangeably, but efforts are being made to separate the two terms as GCC contains tools to compile more than C.
Documentation in this section will refer to gcc, the GNU C compiler. The intent is to provide a quick lookup of common actions and options. The GCC project has detailed documentation at https://gcc.gnu.org which document installation, general usage, and every command line option. Please refer to the official GCC documentation on any question not answered here. If a certain topic is unclear in the GCC documentation, please request specific examples.