Horizontal style it's a style that puts all user's info above his post content,
unlike the default vertical style that puts user's info to the side of his post's content.
The horizontal style was the default style in vBulletin3, the style continued to exist in vBulletin4 as an option but not as the default style.
In vBulletin5 there is no build-in option to enable horizontal style for posts (though it is still used for the responsive version).
This mod will change your posts design to horizontal style.