Knowledge Management system (IT Support/Management)

For anyone who has implemented a ‘knowledge management’ system, specifically regarding ‘knowledge’ from an IT support/management perspective, can you give some examples of the types of knowledge articles you capture in your KM system? How regularly are they reviewed and updated to ensure the content remains relevant? Do you refer to the system as a knowledge management system, or does your team use some other term?
or if you were starting a knowledge management system from scratch, would there be some industry standard 'useful to all' knowledge articles to capture as a priority?
I presume it must be a well structured base of articles, so even just knowing the categories/sub-categories would be an insight.