An insider story features protagonists who are already part of the world in which the narrative takes place. Their stories often involve a struggle to survive and pursue their goals while dealing with the strictures and demands of that world. It’s not uncommon for their understanding of that world to change dramatically – sometimes even resulting in a conflict of loyalties.
An example of this is The Insider, a film starring Russell Crowe as Jeffrey Wigand, who worked for the tobacco industry and discovered that the company knew more about nicotine’s addictive properties than they admitted. The movie follows Wigand and CBS producer Lowell Bergman as they fight to get their story on 60 Minutes, despite attempts by the Sheikh of Hezbollah’s bodyguards to discredit and suppress it.
A potential pitfall of insider stories is that they can become boring if the protagonist is completely comfortable with the Evil Foundation upon which their fictional world exists. This can make them hard for readers to connect with, and may turn them against the story before it gets far enough to begin subverting those foundations.
One way to avoid this is to have the protagonist narrate the story with a first person perspective, but not explain every little cultural tidbit about the world they’re in. This is done in a lot of sci-fi and fantasy literature, and it can work very well if handled properly. It’s best not to overdo it though, or you risk making your story a series of inside jokes that only your readership will understand.