Triggers
A trigger is the moment a flow starts.
The core triggers: a Webhook call arriving, a Schedule, a Cron expression, an Interval, a Manual test from the editor, a Form submitted on one of your screens, a Flow called by another flow, a Feed check. Beside them, services bring their own (Slack message posted, Stripe payment completed), listed on each service's page.
The per-trigger pages land as this machinery finishes building.