uWSGI is the application server that runs the DefectDojo application, written in Python/Django, to serve all dynamic content.
Tasks like deduplication or the Jira synchonization are performed asynchronously in the background by the Celery Worker.
In order to identify and notify users about things like upcoming engagements, DefectDojo runs scheduled tasks. These tasks are scheduled and run using Celery Beat.
The Initializer gets started during startup of DefectDojo to initialize the database and run database migrations after upgrades of DefectDojo. It shuts itself down after all tasks are performed.