Database prefix 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 j73172_ to represent the prefix. This will be replaced by the real prefix during runtime by Joomla. Reference: http://docs.joomla.org/Glossary
Component A component is a kind of Joomla! extension. Components are the main functional units of Joomla!; they can be seen as mini-applications. An easy analogy would be that Joomla! is the operating system and the components are desktop applications. They are usually displayed in the center of the main content area of a template (depending on the template). Most components have two main parts: an administrator part and a site part. The site part is what is used to render pages when being called during normal site operation. The administrator part provides an interface to configure and manage different aspects of the component and is accessible through the Joomla! administrator application. Joomla! comes with a number of core components, like the content management system, contact forms and Web Links. Reference: http://docs.joomla.org/Glossary
JED (Joomla Extensions Directory) The official directory for all components, plugins and modules available for use with the Joomla platform. This database is maintained by the Joomla developers.
