It is meant to be used by audio engineers in order to adjust the playback equipment so that the accompanying media is at a comfortable volume for the audience.
It is sometimes played in sequence between a 100 Hz and 10 kHz tone to ensure an accurate response from the equipment at varying audio frequencies.
This is also the "bleep" tone commonly used to censor obscene or sensitive audio content.
More sophisticated tuners offer a choice of other reference pitches to account for differences in tuning.
[1] For standardized test signal levels and frequencies, see MIL-STD-188-100 for United States Department of Defense (DOD) use, and the Code of Federal Regulations Title 47, part 68 for other Government agencies.