Cataloging gibberish

My teacher for Advanced Cataloging keeps saying that cataloging is so cool because it's like a secret language that only us catalogers can understand. But man they could at least make the rules easier to understand!

Take this one for example:

--Documentation

Use as a topical subdivision under topical headings for works on the processes by which documents on those topics are made available.

I get "use as a topical subdivision under topical headings" but not " for works on the processes by which documents on those topics are made available."

What does that even MEAN???

And on a related note, I find it incredibly amusing that there is a Library of Congress Subject Heading for "Drinking an airplane accidents."