Understanding Environment Variables of $HIP And $JOB

[Ilia]

      Sorry to bother everyone, I know this is a very basic question, but it stuck me for a long time, so that every time it would give me trouble in mind. That is a clear explanation of the two environment variables of $HIP and $JOB.
     I've read a lot of tutorials and explanations. I basically know that $HIP represents the parent path of my current scene file, and $JOB represents the parent path of my current project folder. Is that right?
     But in my houdini practice, this is confusing. When I create a new project, I can clearly see what my $JOB means. But that doesn't explain where the $HIP points to. When I create a 'file cache node', it is obvious that $HIP, which is my project folder, is displayed on the upper level of the geo folder. Isn't that a same path with my $JOB?
      I have attached my screenshot below, which shows my directory structure. I use the default folder structure generated when Houdini creates a new project. I made a little change, but it should be the same basically.
     I hope someone could give me some advice.

 

Thanks!