If you’ve ever been curious enough to look through your system’s root directory, you may have found yourself a little overwhelmed. Most of the three-letter directory names don’t tell you much about what they do, and if you ever needed to make important modifications, it would be tough to know where to look. I’d like to take those of you who haven’t ventured much into your root directory on a brief tour. Before we embark, here are a couple of tools that will allow you to dig through anything interesting you find on your own later.
From: Linux Insider