The Featured Upgrade option allows you to promote one of your ads to "Featured" status. These ads will be labeled with a "Featured" banner and will be shown on the main page of the site as well as being shown first in search results.
Ads are shown in order of how "new" they are. As ads get older, they get pushed down in the search results. A Bump-up allows you to push your ad back to the top of the listings as if you just posted it and it was "new" again. Slick, right?
Custom tags allow you to get creative when listing your horse. You can post short phrases such as "Show Horse", "Kid Friendly", etc. These custom tags are searchable and allow you to add unique characteristics that help to differentiate your horse from all the others.