title: What is the relation between .ycm_extra_conf.py and Exuberant Ctags
body: <p>I am currently in the middle of switching my C++ based IDE from XCode to Vim.
  I have been reading about the Vim plugin "YCM" and it requires the presence of .ycm_extra_conf.py in the source dir. I am using YCM Generator to generate the .ycm_extra_conf.py and Ctags for generating Tags. My questions is what uses Tags ? Does YCM have any use for Ctags (Which collects all the definitions and important information about the code) ? Does YCM using tags generated by CTags in any way ? Does the generation of  .ycm_extra_conf.py require the presence of Tags ?</p>