While any group can have one, internal knowledge bases are usually used by companies to capture knowledge that employees need in order to properly do their jobs, and can include information on:
The most important thing to keep in mind when building an internal knowledge base is to keep the information up-to-date, easy to understand, and easy to find.
Information should be short and relevant to prevent confusion in its interpretation. If possible, avoid burying information in longer, multiple topic pages or documents. Where you can, create information on a single topic.