What is Joomla in PHP?

Hello All Seniors, Can anyone tell me exactly what is Joomla in PHP? I have visited some sites to learn it but still, I am confused or any sites or books to learn more about PHP?

Joomla is not a component of PHP, nor is it an extension.

Joomla and Wordpress are called Content Management Systems (CMS), whereas Dolphin is more a a social networking script. Joomla and Wordpress are similar to each other, but Wordpress has become the defacto standard. To build a Dolphin-like site with both, you have to add modules, some of which cost money.

I ran a Joomla site once for an organisation.  I found Joomla powerful but also more difficult in the structure; takes some learning to understand the structure.

I suggest joining a Joomla forum to get answers.