What does PHP actually do?

Question

I started learning HTML and CSS cause I wanted to build websites. And now PHP comes into play. Can I have a description of how it works please peeps.

Answer 1

While HTML and CSS are used for structuring the webpage and js is used for making interactive webpages
PHP is used for making login and signup systems work on websites, retrieve user info from databases, providing dynamic content and so on
So basically PHP adds interactivity with the web server

Answer 2

yeah, but js will be used on the client-side and php on the server-side.

Answer 3

so are js and php consequently doing the same job? cause both add interaction.