I stumbled upon this great example how to write a MySQL LEFT JOIN today. It explains pretty well what they are used for and how to write one. Check it out.
http://www.tizag.com/mysqlTutorial/mysqlleftjoin.php
One thing that should be explained better is what a regular JOIN is. You don’t have to say the word JOIN, but basically when you select from multiple tables, you are doing a JOIN.
