This page is the Knowledge-base home in CRM. It shows article categories along with the top 5 articles from each category. You can click a category title to get the full list of articles on that subject.
Helpdesk administrators can control which articles are shown in the "top 5" list by reordering articles in a category (to do that simply go to the KB category page and click "reorder articles").
You can also "Search" for particular articles, just use the search box on top and hit "enter", or browse articles by tags that are shown at the bottom (along with the article count under each tag).
If you're viewing 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 helpdesk ticket to the knowledge-base by clicking the "publish to KB" link on the ticket page under "more" menu.