Components, as you already know, are fairly complex and have the ability to display different information in different ways.

For example, the Articles Component (com_content) is able to display a single article, or articles in a category, or categories in a section. Each of the ways of representing the different types of data (an article, or a category, or a section) is called a "view" (this comes from our MVC terminology).

Most components will have many views. However, the view doesn't actually display the output. This is left up to what we call a "layout" and it is possible for a view to have a variety of layouts. It is very important to distinguish between the role of templates and the role of layouts. The template sets up a structural framework for the page of the Web site. Within this framework are positions for modules and a component to display. What actually gets displayed is governed by the module layout, or the combination of view and layout in the case of the component.

The main thing to remember here is that components can have multiple views, and each view can have one or more layouts. Each view assembles a fixed set of information, but each layout can display that information in different ways. For example, the Category view in the Articles component assembles a number of articles. These articles could be displayed in a list or in a table (and probably other ways as well). So this view may have a "list" layout and a "table" layout to choose from. Modules, on the other hand, are very simple. They generally display one thing one way. Modules don't really have views but they do support a layout. Some developers might even support a choice of layout through module parameters.

The module positions are displayed by adding tp=1 to the URL (eg, index.php?tp=1). Using this you can clearly see where the module output is contained within the overall template, as well as the main component output. However, what is actually output in those regions is controlled by the layouts. So, let's make a clear distinction between the template and the layout if we talking about a Joomla site.