A Featured Block Shortcode is a block that has a unique style in every theme, and is meant to highlight some content that you have. It is usually styled to correspond theme design, and its appearance may differ significantly from theme to theme.

Whatever the Featured Block is styled like, there is always an option of adding a button to it:

See the standard Featured Block editor in admin panel:

featuredblock-1

Yet, in some themes, a Featured Block shortocode has some additional features, like block color choice and/or button icon direction choice:

featuredblock-3