... is pretty basic - just a folder containing some special file (e.g. a VCS marker or a project descriptor file like pom.xml or Gemfile). Projectile will auto-detect pretty much every popular project type out of the box and you can easily extend it with additional project types. Projectile tries to be practical - portability is great, but if some external tools could speed up some task substantially and the tools are available, Projectile will leverage them.