PHP:
->PHP is an acronym for “Hypertext Processor”.
->PHP can also be called as an Open-source Scripting language.

Some Websites which uses PHP:

->Wikipedia:
This website uses PHP as programming language along with MySQL/MariaDB as thier Database Backend. This website was initially written in UseModWiki(coded using perl) and then was rewritten in PHP to execute faster.

->WordPress:
WordPress is one of the largest content management system which uses PHP to interact with databases to fetch data and information.In this website PHP is generally used to fetch Data & Information such as some key components from a database and gives a output in an static HTML.