Ok, before I get started I want to say that I already asked about php basics about a month ago and got great responses from very skilled webmasters in here. I have a few questions that I find important to ask, and I would really apreciate it if some of you could take the time to answer any of them.

1- I know that in order for php to actually be able to communicate with a database the file needs to be named.php even if its 99% html. My question is if html will still work properly if no PHP is typed inside it but I still named the file "xxxx.php". For example, lets say that I have a complete website made in html and only one of the pages includes php codes. But I dont want the site to have .html in some pages and .php in others. I want the whole site to be .php. Will the html code work even if the whole site is .php or would it be better if I only name the page with php .php and have the rest of the pages that have no php remain .html? (Sorry if that was a bit confusing)

2- How exactly does a webmaster receive the info people type in the php forms a website has? I mean, do you place your email in the code and receive the info there, or is it more complex than that?

3- When I make a website on html, I just go to the webhost and place the images in the "images folder" and the code in the "public html folder".But how does it work with php? Lets say I have just a bit of php code inside an html page and I want that bit of php coding(a contact form for example) to work properly. Do I have to make any other changes on the webhost to get that php code to work?

Thanks in advanced for reading this.