All comic books have a front cover meant to entice potential buyers to purchase the issue. The covers always present either a gag situation with one or more of the book's primary characters, or a situation taken more or less from the stories inside. Carl Barks made numerous covers using both options - and he liked the task. It was fast and easy work (he only had to make one drawing whereas a story page typically contains 8), and it was well-paid work (a cover drawing paid the same as a whole story page).
Often other artists made covers that illustrated one of Barks' stories inside the issue, and a collection of those are presented in the first sub-pages. Furthermore, you are presented to a special page about what might contain elements of front cover plagiarism. All sub-pages present the covers in chronological order.