The 'cmake' file format is not a traditional data or document file but rather a configuration and build script file used by the CMake build system generator. CMake is a cross-platform, open-source meta-build system that generates native build files (like Makefiles, Visual Studio solutions, or Xcode projects) from platform-independent configuration files written in the CMake language. These files, typically named 'CMakeLists.txt' or sometimes just 'CMakeCache.txt' or other files ending in '.cmake', contain commands, variables, and logic that define how source code should be compiled, linked, and installed for a specific project. Developers use these scripts to manage complex build processes, handle dependencies, set compiler flags, and ensure that the software can be built consistently across different operating systems and development environments. The language used within these files is declarative and procedural, allowing for sophisticated control over the build process, making them crucial for modern C/C++ and other language projects.