How to create a custom plugin

Sorry for the ignorance

I understand it's possible to create a custom plugin and use triggers in it.

Can someone please explain in details how to do that?

I looked in documentation and in the forums and couldn't find the 'how to...'

Thanks

Hi,

The introduction of our developer documentation has a link to the Joomla documentation which explains how Joomla plugins work and how to develop them:
docs.joomla.org/Portal:Plugin_Development
You need to understand that before you can understand the developer documentation we have available.
The main page that you'll want to read is this one:
docs.joomla.org/J3.x:Creating_a_Plugin_for_Joomla