Wrapper A Joomla module that allows you to “wrap” directly other Web sites for display on your Joomla site at a specific location as determined by the Module Position and the Pages Items section. The web page is inserted as an Inline Frame (also called an Iframe) into the web site layout template.
Template A template is a type of Joomla! extension that changes the way your site looks. There are two types of templates used by the Joomla! CMS: Front-end Templates and Back-end Templates. The Front-end Template controls the way your website is presented to the user viewing the website's content. The Back-end Template controls the way your website's administrative tasks are presented for controlling management functions by a Joomla! Administrator. These would include common tasks such as: user, menu, article, category, module, component, plugin and template management. Reference: http://docs.joomla.org/Glossary
Language Key The name for a specific piece of language-specific text in a Joomla application. KEY = Value: where “KEY” is a string to be translated and “Value” is the translated string. In a Joomla program, language keys are used instead of literal language strings. The actual text is substituted at runtime based on the currently active language.