olemus
(1a) tagaplaan otseses (pilt, heli) tähenduses
Wiktionary:
2. part of the picture that depicts scenery to the rear or behind the main subject
4. a less important feature of scenery (as opposed to foreground)
There was tons of noise in the background.
The photographer let us pick a background for the portrait.
5. (computing) the image or color over which a computer's desktop items are shown (e.g. icons or application windows)

https://wikidiff.com/foreground/background
https://en.wikipedia.org/wiki/Background_noise
https://en.wikipedia.org/wiki/Background_music

(1b) samaaegne teisejärguline protsess

Wiktionary:
6. (computing) a type of activity on a computer that is not normally visible to the user
The antivirus program is running in the background.

ISO/IEC/IEEE 24765:
töödete plaanimisel töötluskeskkond,
kus täidetakse madala prioriteediga protsesse
või kasutaja sekkumise vajaduseta protsesse
=
in job scheduling, the computing environment in which low-priority processes or those not requiring user interaction are executed

https://en.wikipedia.org/wiki/Background_process

vt ka
- taustakontroll (1)
- taustakontroll (2)
- taustatrüki jätkumine fotol
- taustteaberünne
- taustteave, taust (2)
- tausttegum; tausttöö
- tausttöötlus