How do I create a dynamic topic-based landing page?

Go to Taxonomy in the main navigation on the left side of the screen. Click Topics.

Click Add Taxonomy.

Add the name of the Topic in the Title field. If desired, add a description. Upload an image if you'd like it to appear on the page.

Select whether you want it Hidden, which means it won't show up in Navigation, or Selectable, which means ....
Save changes.
Icons within the list of Topics indicate whether something is Hidden (eye) or  Selectable (turned-on icon).