In plain language
When something happens, the system announces it, and every interested process responds on its own.
Example
An “order placed” event triggers separate workflows for the receipt email, inventory update, and accounting entry.
Related terms
Webhook · Trigger · Queue · Idempotency
Common misconception
Event-driven does not mean events arrive once and in order; most systems can deliver duplicates or out-of-order events.
Implementation guidance
Give every event a unique ID, make consumers idempotent, use queues to absorb bursts, and keep a record of events for troubleshooting.