CMake is a cross-platform, open-source build system that is used to manage the build process of software projects. It provides a way to automate the compilation, testing, and packaging of software across different platforms, making it easier to develop and maintain code that can be compiled and run on different systems. CMake uses a script-like language to define the build configuration and dependencies, which makes it easier to create and manage complex software projects. It’s a widely used tool in software development, especially in the C++ community.