Usually, each folder in the root of the website is core (but not necessarily).
Core — is a collection of modules, templates, and virtual root folder.
The framework is the core, your folder will also be the core (you need to create it), each core should be stored in separate repositories.
In the simple case, you will have only two cores, for example:
It is possible to add additional cores.
All active cores need to be registered in the /config.php file (the 'cores' key).
When the framework class
The following folders may be located inside the core: p>
root— virtual server root templates— contains templates folders modules— contains modules folders