CMakeLists
The CMakeLists files define the source files and targets of the project(s). The most important CMakeLists is located in the root directory. It creates the project(s) at scope and contains essential information such as the required compiler, as well as the versions of CMake, C++ and libraries.
CMakeLists in subdirectories define CMake behaviour for the folder contents (e.g., copying of input data to the build directory).