a page with an .html extention is what we call a static page. Now the connectivity between html pages and a daataabase (mySQL) needs to be dynamic. Thus instead of saving our pages with a .html extension, we use .php, .asp ....etc
They will still contain html coding, however you be able to create a connection script to the database and be easily to manipulate data from your page.
Are you familiar with any other coding languages?