If you’re new to Linux there is no doubt that the Linux directory structure can be rather overwhelming. Many of the folders are made up of titles that are just three or four characters in length, and when it comes to Linux it is better not to assume you know what one of the folders is used for.
I recently stumbled across an excellent guide by The Geek Stuff that tries to make it a little easier to understand the Linux directory structure. They have a nice graphic (a snippet of it is above) that gives you an overview of each of the folders, and then they dive into each one a little more by providing examples of how it may be useful to you.
The Geek Stuff has all kinds of other Linux articles that are useful as well, such as their 50 UNIX/Linux Sysadmin Tutorials and 15 Awesome Cron Job Examples. There is a wealth of Linux information on the site, and as a result I’ve learned quite a bit from them.