Plug-In Manager shows a list of all of the Plug-Ins installed with your Joomla Installation. Plug-ins are Joomla Extensions that respond to a trigger, they kick in when something wakes them up.

Many of the Plug-ins that you see in the list will be the ones that are installed with the Joomla initial installation. these are Extensions for things such as the Authentication, Content, Buttons, Search, System controls and User Controls. Some default Plug-ins are disabled.  You may find that you will need to enable them for some 3rd Party Extensions to work correctly or for a specific functionality that you need on your site.

When you click on the name of the Plug-in in the list you will get to a screen with the settings for that Plug-in. some Plug-ins will have all sorts of things you can change, others are very simple. Unless you need to change these settings for some specific purpose, it is best to leave well enough alone.

Plug-In Examples

One Plug-In that may require editing is the Captcha-ReCaptcha Plug-In.  What this Plug-In does is control the appearance of the Captcha-ReCaptcha box on forms such as the Contact Form or the Registration Form.  Captcha-ReCaptcha help to reduce spambots from filling in and submitting forms throughout the web. Captcha-ReCaptcha requires that someone reads and interprets the squiggly letters before submitting the form.

In order to make use of Captcha-ReCaptcha, you must go to Google's Captcha-ReCaptcha site, register your website and get a Public Key and a Privat Key to enter into the Joomla Plug-In Basic Options tab under Captcha-ReCaptcha. You may also select the basic appearance of the ReCaptcha box.

3rd Party Plug-Ins

When you install 3rd Party Extensions through the Extension Manager, the installation process will often install new Plug-Ins.  In some instances, you need to Enable the Plug-in. The reason that they don't install as already enabled is because they may not be required for basic functionality for the Extension and there is no reason to use system resources unless it is deemed necessary.