What is it?
can be a group or individual, who attack other parties whom they strongly disagree with on some principle/s, whether what they do is legal or not. They vary in resources, and the skill level varies widely.
Why is it mentioned?
These are an important group to consider, especially for organisations that know their actions could draw the attention of these hacktivists. They are unique in that the usual deterrents may not work, as they will target the organisation with a belief they are carrying out the greater good.