Here you go !
What is different between HTML and PHP?
HTML/CSS is what the website is made out of the interactions like color changes or movement based on the cursor is jQuery these three elements make up standard website effects and visuals. Now PHP doesn't make up anything visual. PHP communicates with servers. For example, to login into Facebook the PHP script sends your input for the login, checks with the main Facebook server to see if its right, if its wrong it gathers the HTML to load the page it does when the input is wrong, now if its right it gathers the HTML and loads your news feed and other various things on Facebook. If a website requires no server or login there should be no PHP if there's a server then it has PHP. Think of PHP like a messenger, they bring data from the original source and then to the main source back and forth.
HTML use for create static website or design front end of website, If you want to develop your website dynamic then we use php language.
HTML (Hypertext Markup Language) is a markup language, and PHP is a server-side scripting language. Where HTML is the backbone of all web development and one of the most fundamental technologies used in front-end web development, PHP scripts execute on the back-end, manipulating data on the server and outputting content to a webpage based on a user’s inputs. Together they make dynamic websites possible.