The fold refers to the point where the post is being cut off on from the view of the visitors on your blog. The user can scroll down to view the materials below the fold but the visitor won't be able to see it immediately when they land on your site. The content that appear above the fold should be given priority because they have higher value in SEO. For example, you should avoid placing too many ads on the areas above the fold as it will cause distractions for users. If there are too many ads above the fold, you may get Google Panda penalty. The Top Heavy algorithm will rank your website lower if there are too many ads above the fold.