What is MECHANISM in the event dashboard?

I am integrating Sentry in a React app, and I created an ErrorBoundary that catches any errors and sends them to Sentry. I am testing it by throwing some errors in the app and the question is, every time I catch one error, I see two events for it in the Sentry Dashboard. The only difference between them is the MECHANISM values. One has Mechanism ‘instrument’ and one ‘generic’. So what is the difference between these two and why are both being sent?