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Extensions, modules, components, plugins - what they are

"Extensions" are programs that you can plug in to Joomla to make it do more.
Joomla extensions fall into three categories:
- modules
- components
- plug-ins
The differences between them can be confusing. This is understandable!
- There is considerable overlap among categories of extensions.
- Complicating matters even further, Joomla extensions can contain any mix of modules, components, and plug-ins.
- And one extension developer may decide to do some task, such as displaying a site map, with a component; another may use a module.

What's the difference?

	components	modules	plug-ins
The basic idea	Components are essentially what you see in the "main" portion of the page. Joomla is designed to load and run exactly one component for each page generated. Consequently, Joomla's core content management functionality is itself a component.	Modules complement the content contained in a component; they are not intended to be the main substance of a page.	A plug-in is a piece of code that is used throughout the site. Often work on both the data that users send to Joomla and the data that Joomla sends to users. An example would be a special type of WYSIWYG editor that accepts data from users as they edit the text and that passes data to Joomla as well. Plug-ins can focus on either the front end or the back end. Some back-end plug-ins, such as those for online shopping carts, have very complex administrative interfaces.
Usage	The content of a page. It may even be a full application (Say, a form with some programming behind it that puts info in a database).	Modules typically make up the elements of a sidebar or content menus. Joomla also supports content modules, which involve no programming and can be displayed alongside coded components.	To format the output of a component or module when a page is built. Could also be used to extend the results found in a core component. For example, you enter a search term in the module, and it displays the results in a component.
Display in	The content area of a page	The "periphery" of a page: Sidebar, header, footer, etc.	Anywhere
Accept input	Yes – can accept all kinds of input, from article submissions, to user comments in a forum.	None, or minimal – read-only (such as the Who’s Online module) or accepts only minimal input (such as the Polls module).	None, or minimal.
Examples	An article A list of articles A site map Upload pictures or videos Custom form/application	A widget on the page, like a poll or a calendar. Menus are modules.	keyword highlighting article comment boxes JavaScript-based HTML editors.
How many on one page	One only	Multiple	Multiple
Has a page "position"	No - it is the the content Placement is at the `<jdoc:include type="component" />` in the page template.	Yes	Yes?
Its filename begins with	`com_`	`mod_`	`mos_` or `bot_` (used to be called "mambots")
Find	http://extensions.joomla.org
Install	Extensions menu → Install/Uninstall
Configure and Manage ("back-end controls", "administration")	Components menu → <component name> can have a very complex administrative interface complete with many tabs and screens. commonly used to create and update records in database tables. typically anything, provided it is programmed in PHP.	Extensions menu → Module Manager limited, typically consisting of things such as basic formatting, where the module appears on the page.	Depends on the plug-in – check its documentation.
Access (Display on website)	Link a menu item to it: Menus → Menu Manager Select menu you want to use Click New button Components will be listed in the node tree. Click the component name and proceed as for adding any menu item.	With `position` defined in template.	With `position` defined in template. ?
	components	modules	plug-ins

Know more

General info:: www.tibetangeeks.com/technologies/web_development/; Tech info for Tibetans; About web development, Joomla, and other CMSs

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