Modules are the core of your Zikula site. Almost everything you see here is generated by a module, or managed by a module. Consider your Zikula site as your computer's desktop. Zikula is your operating system. Modules are individual applications, such as a word processor or your internet browser, while blocks would add secondary function, for instance an instant messenger or weather alert widget.
There are essentially two types of modules: system modules and value addons modules. System modules are essential for smooth operation of Zikula and are contained in the system directory. All other modules are contained in the modules directory and give you additional services depending of the specifics needs of your sites.
On the user side, modules present and organise content for you. For instance, the News module takes articles you add to it, organises them and displays them to your site visitors in a number of different ways - sequentially, in an archive form or even through an RSS feed. All of that is generated for you by the News module.
There are modules for almost any purpose. From managing simple HTML pages, to a forum, a contact form, a gallery, downloads management - it's all there. You simply have to find and install a module for your purpose. This very page you are reading now is generated by the 'Tour' module (which you can uninstall any time).
Getting New Modules
Placeholder for notes on the new extensions database and EasyDist.
Installing and Removing Modules
Zikula comes with an easy way of managing the modules you have installed. This is provided through the Modules section of the Administration Panel. Here, you see a table of the installed modules, their current status, and to the right buttons for activating (usable by you and your site visitors), deactivating (data is saved, however the module is 'switched off') and removing (deletes all stored data and prepares for filesystem removal).
Removing a module is very simple - just navigate to the Modules section of the Administration Panel, find the module you wish to delete and click the 'remove' image. Once you've done that, just log into your FTP and delete the module's files. You must always remove the module from Zikula before your file system, or inconsistencies may arise (for security reasons Zikula cannot delete the files for you, but they may lie there dormant).
In general, to add a module, extract it in your computer, then upload the module folder using FTP to the 'modules' directory of your Zikula site; then go to the Modules section of the Administration Panel, and click the regenerate link at the top of the page. This allows Zikula to detect new modules you may have uploaded. Once you have done this, find the module you added in the table below, then click the initialize image (NEED SCREENSHOT). This installs the module and gets it ready for use. Finally, active the module, using the activate image. This causes the administration link to become available so you can explore your new module. Modules come with documentaion, do read it first, as installation needs may vary.
More to come in this tutorial soon. If you could help us to expand our documentation, please post in the forums at community.zikula.org