Completing Activities is a way to earn Cash and Respect, as well as City Takeover territory. Diversions only give Respect, but most are tied to Challenges which award cash when performed under certain conditions.
Unlike previous games, Activities no longer have increasingly harder levels, but are instead separated into six instances over two Districts and ranked by difficulty. Completing "easy" instances of each Activity unlocks the "medium" and "hard" instances in each District.
There are 56 instances of Activities in Saints Row: The Third. 54 of these are nine separate Activities split into six instances, with the only exception being "Guardian Angel", of which there are only two instances.
Individual Activities do not have cutscenes or introductions.
At least 1 of each type of Activity is compulsory. 14 Activity instances required as part of the storyline and are counted as both activities and missions in regard to game completion. This includes 12 "easy" Activity levels, as well as both instances of "Guardian Angel". There are only 6 "easy" activity levels which are not compulsory.
Compulsory Activity groups have standalone start and end cutscenes which are started like missions.
Individual Compulsory Activities have introductory phone call when started via the Cellphone, but which are not played if the activity is started via the activity marker.
Prompted upon stealing a car with one or more passengers, there is a prompt to start the Hostage diversion. The aim of this diversion, is to drive around for a certain amount of time, without slowing down enough that the hostage can escape.
Territory ownership is rewarded upon completion of Activities, taking over Gang Operations, and by buying stores and properties. Saints-controlled territories spawn random Homies and increases City Income.
Saints Row: The Third requires 14 specific activities to be played, at least one of each type. This is the first game in the series to do this. In previous games, there was a choice of which activities could be completed to earn respect, and it was possible to complete the storyline and completely avoid playing a specific of activity.