Sponsored posts are one with thumbnails on top of each page. They are similarly sized as "Advertise Here" image
Featured posts are one line posts that appear on right side of page, under "Featured" section
Both Sponsored and Featured are free and they will be visible on every page. But since space is limited, we will remove older posts to provide space for newer once.
To attach a thumb nail image for your post
Adding Animated Images(As Thumb (or) in your Post Gallery)