This page is the Knowledge-base home page. It shows article categories along with the top 5 articles from each category. You can click a category to get the full list of articles on the subject.
You can use the "Search" feature as well, just use the box on top of the page.
If you're accessing this page as a helpdesk administrator, you will see the "new article" button that creates a new KB entry. Another way of creating a new KB article is to publish an existing ticket to the knowledge-base by clicking the "publish to KB" link on the ticket page.