Moodle stands for Modular Object-Oriented Dynamic Learning Environment, which explains the background to the plugin structure of the Moodle application as it is all modular.

There are many plugin types in Moodle including authentication, enrolment, themes, course formats, and each of these control an aspect of Moodle such as, an authentication plugin, which enables the administrator to control how users log into Moodle.

Moodle is written in PHP and can be run on a number of web servers that support PHP, including Apache and IIS.

Moodle supports a number of database types including MySQL, PostgreSQL, MSSQL, Oracle, and SQLite. However, the most supported and tested would be MySQL and PostgreSQL.

Moodle also stores files in a directory on the server, which is referred to as the moodledata directory. Moodle stores all of its files in this directory including temporary files, session data, and user uploaded files.

Always check the minimum server requirements for the version of Moodle that you are planning to install. These are found in the release notes on the MoodleDocs site. The latest version will be found at https://docs.moodle.org/en/Installing_Moodle#Requirements.

So, when considering the Moodle installation, you must consider the PHP files, the moodledata directory, and the database.