I have made many researches about this CMake macro, but I cannot understand what the task of this macro is. I have also read CMakeLists.txt tutorial in the link http://wiki.ros.org/catkin/CMakeLists.txt. In this tutorial, the purpose of this macro is not clearly specified, I think.

The most informative page for this macro is this link: https://docs.ros.org/api/catkin/html/dev_guide/generated_cmake_api.html#catkin-package

However, this is not sufficient, I think. For example, I could not understand why we do not write all packages in findpackage() macro into CATKINDEPENDS section of this macro.