The cities really feel alive thanks to the plethora of various side quests you can entertain yourself with. (gamingunion.net)
Rather, between each chapter is an interlude in which various side quests are introduced that delve into the main cast and their back stories. (kotaku.com)
You'll also need to tag supplies and complete various side quests in order to get enough of the necessary items. (rectifygaming.com)