When you're trying to navigate through directories and subdirectories of music, especially on a USB drive, the buttons are difficult to press and not everything can be done from the steering wheel. (autolist.com)
To achieve this, I let iTunes reorganize its library (File > Library > Organize Library), so all the books are in a single «Books» directory, with a separate subdirectory for each author. (safaribooksonline.com)
I'm also assuming that he's referring to firms that develop multiple practice area blogs and position those blogs as subdirectories (or subdomains) under the firm's principal website. (stemlegal.com)