Template; This is a sub-programme that you can add to Joomla (to use instead of the basic templates included within Joomla). It integrates with Joomla so you use it directly from the Joomla control panel.

The template enables you to customise the ‘look and feel’ of your website by
• Enabling you to put things where you want them to be on your website.
• Giving you sets of features which look good together, and which you can choose to use on your site, for example, the menu structure, backgrounds, tabs, banners, photo galleries, slideshows, sliders, popovers, typography, (please add to this list)

A Joomla Template - this controls the appearance and layout of a site.

It provides the structure for plugins, modules and components combined with
cascading style to display the site as required.

The template may take advantage of using a framework

Templates are used both on the Front-end of the site and also the Back-end (Administrator) side of Joomla

Different templates can be assigned to different pages of a site or as a different variant of a template

Templates are controlled by the template manager styles page and can be duplicated or deleted there - if olny one version of the template is left it can only be deleted via the extension manager

Cheers
Paul