Celery can be somewhat difficult to understand due its distributed architecture. Here's a high-level diagram showing a typical Django-Celery setup:
How a typical Django Celery setup works
When a request arrives, you can trigger a Celery task while handling it. The task invocation returns immediately without blocking the process. In fact, the task has not finished execution, but a task message has entered a task queue (or one of the many possible task queues).
Workers are separate processes that monitor the task queue for new tasks and actually execute them. They pick up a task message and send an acknowledgment to the queue ...
