Real clear answers there guys :rolleyes:
HTML is the language understood by your web browser. It tells your web browser what the page content is, and, with the aid of CSS, how it should presented to a visitor. It is known as a mark-up language and quite literally just describes content.
PHP provides more power over your HTML output. It's a server-side language, which simply means it's processed on the server, rather than a visitors computer. The ins and outs of a programming language are quite complicated, but simply put PHP provides a means of processing data and returning browser readable HTML. This data could be from config files, databases, user input, etc.
Hope this makes things a bit clearer