In order to promote any image on Facebook (share graphic or ad), it must comply by the 20% rule. This means that when overlaid by a 5×5 grid, text only appears in 5 or fewer of the boxes.
Videos are able to get around this rule by uploading a custom thumbnail which is 20% compliant. Facebook also favors videos by showing it to more of your audience, resulting in increased engagement.
Used to gain likes for your Facebook page
Used to send people to an external website
Video Click Ads
Videos can be wide, square, or vertical and usually have higher engagement