The following article introduces you to 'web application frameworks'. If you don't know what this is, read on and you soon will. But for those of you that are impatient...in a nutshell: A web application framework is a set of code libraries (in our case, that would be written in PHP) that handles/does many of the things that we typically need to do when building database driven websites.
He introduces the layered approach behind using a framework - the separation of concerns. With this base information in place, they look at the Zend Framework's components and some of the reasons he thinks about why the framework appeals to him.