What is the new understanding that emerged about the death penalty that recently entered the Catechism?

What the heck does this sentence added to the Catechism mean? > In addition, a new understanding has emerged of the significance of penal sanctions imposed by the state. https://press.vatican.va/content/salastampa/en/bollettino/pubblico/2018/08/02/180802a.html What new understanding? What significance? What sanctions? Is this even a complete sentence?