Background job
Work an app runs behind the scenes after answering the user, such as sending an email or building a report.
What it tells you about a developer
Background job experience means someone has separated urgent work from work that can wait, which is a design decision, and has handled the hard cases: a job that runs twice, a job that dies halfway through, a job stuck behind a backlog. That thinking comes from running real production systems.
An app answers a request in under a second, and some tasks take much longer. Those tasks run as background jobs: the app records the task, replies to the user, and a separate program called a worker runs it shortly after, usually by pulling it from a queue. Common tools include Sidekiq for Ruby, Celery for Python, and BullMQ for Node.