How to Joomla! - Joomla! tutorials and extensions
To allow Registered Users submit an article/news on the Joomla! Front Page, we must create a menu item with function submit article/news on the Front Page. This Menu Item is shown only after users have logged. If you install the sample data, this Menu Item is already available in User Menu.
A user is a person (or group of persons) who has authenticated itself by providing the registration data you requested. Normally, you create user accounts in order to grant access to exclusive parts of your site or allow your visitors to post their content.
After you upgrade from Joomla! 1.5 to 1.7, the old template of Joomla! 1.5 can not be used anymore and you have to reinstall the template is compatible with the new version of Joomla. But if you want to use your old template with Joomla! 1.7, you can try converting them to be used with Joomla! 1.7
Joomla extensions are components, modules plugins, templates or languages that extends your Joomla! installation. They come included in Joomla core or can be provided from 3rd party developer. All extensions are installed through the extension manager.