Tanks and Active Mitigation in World of Warcraft: Legion

Someone recently made a post on MMO-Champion asking whether a specific ability counted as “Active Mitigation” and he received a lot of misinformation. Apparently, many players have an outdated understanding of the term, and to make things worse, the most recently updated Wikis on the topic are 3-4 years old. Yikes! Since I’m so annoying such a helpful guy, I will clear things up.