Modules are assigned to specific pages using a list of menu links that is visible when you edit the module in the module manager (on the right of the page). In older versions of Joomla! this list does NOT include menu links of the type "URL." This is an anomaly from the history of the development of Joomla! carried over from Mambo. Although you can use the URL type for any link, including internal Joomla! links, the original idea was that these would be used for links to external sites which would not display Joomla! modules. Some Joomla! component extensions use URL links (rather than component links with parameters) as a simple way to access specific views of the components.
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