As you chdir around in your CLI, this package will record the places you've visited. Imagine that you've been to /home/longusername/path/which/is/long/blurfl

This package will extend your shell so you can say:

$ j blu

and (assuming nothing more recent has "blue" in its pathname) you'll jump back over to that location.

$ jd blue

Is the same, but a pushd. (Once you have "j", you won't use pushd as much.)