We have tried to mark up the documentation in order of related tasks/roles, and also with an eye on complexity. A piece of documentation may be relevant to several audiences, but normally it's considered relevant to one of the below audiences in particular.

The types of audiences are defined as follows:

End Users

These are the basic users of a Plone site — the content producers. They typically add content, change workflow states and navigate/reorganize/review content.

Site Administrators

Site Administrators are a step up from the End Users in complexity, and typically configure the site settings, add groups and users, and in general use the control panel for setting up the basic site options.

Integrators, Customizers

These people are a step up from the Site Administrators — these people have basic knowledge in how to change a Plone site in various ways - putting a new look on it (skinning/theming), authenticating against LDAP databases, changing the site functionality in simple ways. It is as much about which role these play as well as what skills they possess, Developers are often integrators of some capacity and the other way around. Often have complementary skills like HTML, CSS and Javascript knowledge.

Developers

These people are the ones that write products that extend Plone with content types, behaviour and application functionality - either via code generation or by hand. Normally they possess some skill in Python and know a fair bit about Zope.

Advanced Developers

These people write underlying infrastructure pieces like tools, back-end code and produce advanced products.