The first part of the site page is built from the protocol and the domain name. You can add new parameters using special characters. The question separates the variable from the main site name, and the equal sign gives it a value. This can be used for $_GET requests. If there are many variables in the page name, then they should be separated with an ampersand.
https://site.com
?
veriable1= value1
&
veriable2= value2