Since the HTML/CSS combination is analogous to the data found in a Word document, it is good only for displaying information.
If you want your web pages to do different things depending on the situation, you will need a programming language. For example, some websites want to provide a membership facility where people can log into the site, and access certain information. Other sites provide a feedback form so that visitors can contact them. All these things require facilities that a simple document format cannot do.
Apart from the above difference, from the point of view of a non-programmer, there's not much point asking what the difference is between the languages, say, between PHP and Perl. It would be like asking what the difference is between English and German, or some other human language. They're just different languages that you can use to write web-based programs. Each computer language has its own strengths and weaknesses.
Learning a programming language is vastly different from creating a website whether with a web editor or directly in HTML. Although I have tutorials for things like learning to write programs in PHP (and the other languages), many people will find programming a difficult undertaking, unless they already have a programming background or an inclination towards programming.