olemus
(a) tausttöötlusega täidetav tegum
= a task performed by a system during the time when its primary process is idle
https://www.linkedin.com/learning/linux-multitasking-at-the-command-line/foreground-and-background-tasks
https://en.wikipedia.org/wiki/Background_process
(b) muu tegevuse taustal tehtav töö
= a task performed in the background of some activity