All standard events are tracked by calling the pixel's fbq('track') function, with the event name, and (optionally) a JSON object as its parameters.
You can track custom events by calling the pixel's fbq('trackCustom') function, with your custom event name and (optionally) a JSON object as its parameters.
Based on the facebook-pixel documentation:
https://developers.facebook.com/docs/facebook-pixel/implementation/conversion-tracking#standard-events