If you're relatively new to the PHP world, you may be wondering why there has been so much emphasis put on "magic quotes" in the language's past. If you're not entirely sure what they are (and why to avoid them) take a look at this quick overview from XpertDeveloper.com.
First of let me say that Magic Quotes is deprected from the PHP 5.3 and will be removed completely from the PHP 6. But as a developer you might face a situation when you have to work on application which runs on older version of PHP with some older functionality like rely on Magic Quotes.
They introduce the simple concept behind the magic quotes idea and, thankfully, the settings and code you can use to turn it off. It's been deprecated in PHP 5.3 but some older versions came with it enabled. If you're currently running with it on, it's highly recommended to turn it off and refactor your code accordingly.