Q: What is Code::Blocks?
A:
Code::Blocks is an Integrated Development Environment, aka IDE. Thus, a framework for working with source code and using compilers and linkers (in the case of Code::Blocks, these can be several).
Q: What Code::Blocks is not?
A:
Code::Blocks is not a compiler, nor a linker. Release packages of Code::Blocks may include a compiler suite (MinGW/GCC), if not provided by the target platform already. However, this is provided "as-is" and not developed/maintained by the Code::Blocks development team.