Content management is the engine behind your web site that simplifies the creation, management, and sharing of content.

There is an excellent article on How to evaluate a Content Management System (written by James Robertson) that covers the features of a good content management system in great detail. According to Robertson:

Selecting and implementing a content management system (CMS) will be one of the largest IT projects tackled by many organisations. With costs potentially running into the millions of dollars, it is vital that the right CMS package be selected.

• Integrated authoring environment

The CMS must provide a seamless and powerful environment for content creators. This ensures that authors have easy access to the full range of features provided by the CMS.
• Separation of content and presentation

It is not possible to publish to multiple formats without a strict separation of content and presentation.

Authoring must be style-based, with all formatting applied during publishing.

• Multi-user authoring

The CMS will have many simultaneous users. Features such as record locking ensure that clashing changes are prevented.
• Single-sourcing (content re-use)

A single page (or even paragraph) will often be used in different contexts, or delivered to different user groups.

This is a prerequisite to managing different platforms (intranet, internet) from the same content source.

(This is a complex requirement that warrants a whitepaper of its own.)

• Metadata creation

Capturing metadata (creator, subject, keywords, etc) is critical when managing a large content repository.

This also includes keyword indexes, subject taxonomies and topic maps.

• Powerful linking

Authors will create many cross-links between pages, and these must be stable against restructuring.
• Non-technical authoring

Authors must not be required to use HTML (or other technical knowledge) when creating pages.
• Ease of use & efficiency

For a CMS to be successful, it must be easy to create and maintain content.