title: What is the purpose of a .cmake file?
body: <p>I might be googling wrongly, but I'm unable to find what's the purpose of .cmake files.</p>
  <p>I've just stumbled across the CMake tool for a project I've to work with and I'm having a hard time to understand how it works. I do understand that running the CMake command in a directory containing a <code>CMakeLists.txt</code> executes the commands in that file (along with the commands in the <code>CMakeLists.txt</code> contained in the sub-directories) but the purpose of .cmake files is a lot more fuzzy.</p>
  <p>It seems that they are used to define functions/set variables that are thereafter used in the <code>CMakeLists.txt</code> but I'm not sure. How are they used by the CMake tool ?</p>