An External links section, if any, should always be placed at the end of the article. It should always be spelled that way, never "External Links" or "external links". The term should be used even if there is only one external link.
Wikipedia:Did you know... is a section you can see on the Main Page. Wikipedia:Did you know (WP:DYK) is the project page for the "Did you know" section.
The DYK section showcases new or expanded articles that are selected through an informal review process. It is not a general trivia section. For the discussion page see WT:DYK.
Beginners should consult this Did You Know glossary if they don't understand any of the terms used. Beginners may like to start by looking at a summary of our many rules: this provides links to pages with more detailed explanations (which in turn may link to even more detailed pages).