See Language Override, Alternative Menu Item, Template Override, and Layout Override.

Acronym for Free or open-source software. Software, like Joomla, that is available to use, copy, study, and change in any way without charge. FOSS software typically uses a special software license, such as GPL, that requires any derivative works to also be free.

A user level on a Joomla site that by default can access only the front end. Editors have privileges to post and edit content, but no permission for publishing content.

Page Class Suffix is a parameter in Joomla! content Menu Items. It is set in the Menu Item: [Edit] screen under the "Parameters (Advanced)" section. This will cause Joomla! to either add a new CSS class or modify the existing CSS class for elements in this specific Menu Item layout.

When Joomla! generates a page, it automatically creates pre-defined CSS classes to allow styling of the page. For example, a page might have the element

<div class="componentheading">

To create a new class, enter the parameter with a leading space. For example, entering a space plus "myNewClass" will create a new CSS class called "myNewClass" and it will be inserted as a class for elements in that Menu Item. In this case the example above will be changed to

<div class="componentheading myNewClass">

To change the name of the existing class, enter in the parameter without a leading space. For example, entering "_mySuffix" (no leading space) will cause the HTML to changed to

<div class="componentheading_mySuffix">

Generally, it is recommended to use a leading space to create a new class. This way, CSS styling for this component that uses the standard class names will continue to work. You can use the new class name to add any desired styling to the component without needing to re-create all of the existing CSS code. Note that, if you create a new class name, make sure it has a unique name and doesn't conflict with any existing class names.

Reference: http://docs.joomla.org/Glossary

An extension is a software package that extends your Joomla! installation in some way. A small selection of extensions is included with the default Joomla! installation but many more are available from the Joomla! Extensions Directory.

The term extension is generic and the following specific extension types are available (listed alphabetically):
Component (since ) – adds custom functions to your site that can be selected from menus
Language (since ) – defines an additional language for your site
Library (since ) – provides functions to be used by other extensions
Module (since ) – shows nonessential data in a side box, possibly on multiple pages
Package (since ) – bundles related extensions
Plugin (since ) – modifies content in articles or provides functions to extend other extensions
Template (since ) – define the look, feel, and navigation capabilities of your site

For an overview of the most important extension types and the functionality they provide, see Extension types (general definitions)

Reference: http://docs.joomla.org/Glossary

The database table prefix is a string (a few characters long) prepended to the name of Joomla!'s tables. Using a prefix enables you to run multiple installations of Joomla! using a single database.

The database table prefix can be set during installation. Changing it later is possible, but requires access to the database through a non-Joomla medium or a Joomla Extension such as Akeeba Admin Tools and will cause some downtime.

Extension developers need to use the string #__ to represent the prefix. This will be replaced by the real prefix during runtime by Joomla.

Reference: http://docs.joomla.org/Glossary

Stands for General public license. The most widespread such license is the GNU General Public License, GNU GPL or GPL for short. This software license is available in differrent versions and used by Joomla and many other FOSS projects. Joomla is licensed under GPL2 now.

Options (also known as parameters) are settings used to customise modules, components, plug-ins and templates. The core extensions in Joomla offer many options that the site administrator can set to change the behavior of the site without requiring any programming knowledge.

The main Joomla back-end Control Panel which is used by administrators for managing the whole site.

All critical settings of a Joomla site and server. They include the following: Site, System, Server, Permissions, and Text filters. You can access the Global Configuration settings through the Site menu in the Administration control panel.

Programming technique based on using classes, objects, and methods - an approach to designing modular reusable software systems. Joomla is based on OOP. Solid understanding on OOP is a key plus when working with Joomla programs.

Module positions are placeholders in a template. They identify positions within the template and tell the Joomla! application where to place output from modules assigned to a particular position. The template designer has complete control over module positions, creating variations between templates and the respective Joomla! default positions assigned to modules in the installation sample data.

For example, the module position Left could be defined to be on the left side of the template to display a site navigation menu. So if a module is assigned the Left position, it will be displayed wherever the designer puts that Left module position - not necessarily the left side of the page.

Reference: http://docs.joomla.org/Glossary

A block of PHP code that has a name and it has a property that it is reusable it can be executed from as many different points in a PHP Program as required. Also known as a method (if it is inside a class). Most Joomla code is inside functions/methods.

The database managment system used by most Joomla installations and by most dynamic websites in the world.

The word "core" in Joomla! pertains to the distributed files which are needed to create and administrate a Joomla CMS powered web site. These files can be downloaded from the Joomla website at http://www.joomla.org/download.html. The Joomla "core" also contains some basic functionality to get new Joomla installations working quickly and easily. Included are the user manager, article manager, weblink manager, category manager, contact manager, and menu manager. There is also a template manager with a few basic templates to power the front-end (website/user) view, a module manager with basic modules, plugin manager with basic plugins, and a few other "out of the box" extensions to extend the functionality of a basic Joomla installation. These core's extensions should not be confused with extensions which are available for downloading from the JED (Joomla! Extension Directory).

Reference: http://docs.joomla.org/Glossary

The Joomla site that is accessed by visitors without user privileges. Front page refers to the public home page of your Joomla site.