The cmake executable is the command-line interface of CMake.
To generate a project build system, cmake is typically invoked in the following way:
cd <path-to-build-tree>
cmake [<options>] <path-to-source-tree>
A source-tree means a directory tree of source code files, where the root folder contains a top level CMakeLists.txt file.
A build-tree means a directory tree of generated files. An out-of-source build tree is recommended.