Related Items
Joining content together.
Folders
Folders
in Plone are used as in the normal Windows OS to group different
content together, as the user may deem necessary. A root/home folder is
created automatically for each user when joining the site. other
folders may then be added similar to the other content.
The foldersystem makes it easier to navigate through the content by using the navigation slot
Related Content
On
the bottom of the edit-page, a user may automatically add a link to any
content already on the Plone site, which is reachable by the user
(someone else's private content will be unavailable). Content connected
by this means doesn't even have to be in the same user's home folder!
The related slot, however, works with keywords.

Keywords
Keywords can be added to any content from a list defined by the site
managers. This will automatically bind different content with the same
keywords in the related slot.