How Content Types function in Drupal Commons

The short, bullet-point version of this information can be found here.

What follows on this page is a bit more verbose explanation of the same info.

Drupal Commons provides many different content types. The function of most of them is self-apparent. However, there are some differences. Here is how they vary. An example is provided in each section below; assume that these examples are found on a Drupal Commons community site for owners of boats built by the SeaWorthy Boat Corporation (fictional), and the pages listed are being posted in a group on that site called Wooden boats.

Note that with all content types, a user must be a member of a group before they can create any of these types of content within a group. Note also that other users may, or may not be able to add comments to a given page of content depending on the comment settings set by the original page creator.

Blog

• Blog posts are something for people - or group administrators - to use to express content that has temporary value. They capture updates in the life of a person, or in the activity of a group.  An example title of a personal blog post might be "What I learned when I took my first wooden boat out for a test;" in the same community/group, an example title of a blog post by the community manager might be "Reflections on the September 2010 group meet-up at the dock."
• Note that only the original blog post creator can edit the original "body" of the blog post.

Document

• Document pages basically exist as a container for attached files. For example, assume a SeaWorthy customer modified the wiring harness of their navigation console to add a third-party GPS device, and wanted to share the wiring diagram of the rewired console. The user would create a page called "Wiring harness diagram for adding a (brand) GPS to the Model-123 wooden boat console". This person would add some text to the body of the page, then upload a PDF (or JPG, ..) of the wiring diagram.
• Note that only the original document page creator can edit the original "body" of the document page.

Discussion

• Discussion pages provide a sensible way for users to have discussions with each other. A member of the group starts a discussion by creating the initial page for the discussion, then other users post new comments, or replies to existing comments (to create a threaded discussion.)
• Note that only the original document page creator can edit the "body" of the discussion page.

Wiki

Wikis are different from Blogs, Documents, Discussions & Events in several ways:

• Any member of the group can edit the "body" of the discussion page. This permits all the group members to keep the content of the page up-to-date and correct simply by editing the page and creating / modifying content.  (Much the same way Wikipedia works.) Our fictitious boat company/group might have a wiki page titled "Comprehensive list of boat maintenance tasks for model ABC-123", where every ABC-123 boat owner adds items he/she think are important. 
• User can enter content using special techniques to simplify links (called Wiki syntax).
• If users use Wiki syntax to create links to pages that do not previously-exist, users who click the link (and who have permission to create pages) will be automatically presented with a new page for creating the content of that page (a typical Wiki feature).
• Every time a Wiki page is saved, a new version of that page is created. Users can compare versions to see the differences between pages.

Events

• These can be used to announce upcoming events, such as meet-ups of the group members. This is often most useful for community sites made up of people who are not in the same organization, since (in that case) the group members are unlikely to be using a single organizational calendaring system.

Page

Pages are the normal Drupal Page content type. This is the main defined content type that need not belong to a Group when being created.  It is preserved so that site owners can create content that is of general use for the site, e.g. informational pages, marketing pages, etc.  Commons works in the normal Drupal way with these pages, such that it expects the user to create a menu entry for the page, or link to it from somewhere else.

Notes:

• Breadcrumbs are not created for these pages, since the breadcrumb system is driven off the Groups architecture (not the menu architecture) in Release 1.
• By default only users with the Community Manager role can create Pages.