Plethora is an open-source PHP framework which gives a set of tools to create web-applications.

application - directory used to store all main files related to applications (like config files, classes, views etc.)

framework - all core files of Framework

modules - directory used to store all of the framework modules

public_html - in here you store all public files

vendor - stores main framework subsystems written by other authors (used for composer [https://getcomposer.org]) for example: Doctrine 2 ORM

Use .htaccess or redirect your domain to one of applications located in public_html directory if You want to run app on this framework.

To run INSTALLATION process, just run application and ensure that there will be install.php file in the main public directory of particular application.