What are PHP Files, i need some video tutorials and how i can use them in my website?

[Yousaf]

I need video tutorials for PHP, i mean what does php basically mean and how to use them in website, are they like html codes or something else, i downloaded some php codes but when i preview them in firefox or any other internet explorer, i see only codes, no forms are displayed. And are there some simple html codes for contact forms and comment boxes