This is an aside post. The aside post format can be used when you have something to say, but don’t think that it merits a fully-fledged post. They still look the same as other posts in the single post view, though.
Posts with the aside post format can have post thumbnails as well. The post title will be hidden, but the post thumbnail and the content will be displayed – perfect if you want to post an image with a small note attached.