What is instagram insights?
Also called: native analytics
Instagram Insights
Instagram's built-in analytics for professional accounts, showing reach, impressions, profile visits, and audience demographics for your own account only.
Insights is authoritative for your own account and blind to everyone else's. It is the right tool for first-party questions, which of my posts worked, where my audience is, and no use at all for competitive ones.
That split is the reason most brands run both: Insights for their own numbers, an external tracker for everyone else's.