The Action Type Wiki (or "Wiki" for short) is a feature that allows you to create content to support specific Action Types (matter types). The Wiki can act as an action-type specific "user guide" and allows you to easily create "Articles" which can contain text that you type in, and links to images, documents and other web resources. 
Each Article, or section of an Article, can be linked to Steps, Tasks, or Custom Data elements to provide contextual help for users as they move through the workflow.

Knowledge Base versus "Wiki"

The Knowledge Base feature preceded the Wiki, and there is some potential overlap between the capabilities of the Knowledge Base and the Wiki. The main difference between the Knowledge Base and the Wiki is that the Knowledge Base is a company-wide resource whereas the Wiki is specific to a particular Action Type. Unlike the Knowledge Base the Wiki can be exported with eac h Action Type to create self-contained "Apps" that can be installed in other Actionstep systems.