What is accordion in html? Maybe php...or else?

Answer 1

An accordion is used to show (and hide) HTML content.

https://www.w3schools.com/w3css/w3css_accordions.asp

Answer 2

An exemple in my code 'Which helps the developers' if you want.
https://code.sololearn.com/W0cGWEhdQtwE/?ref=app