So various outlets say different things about this.
Fact is that this is being installed on Android 9+ devices with 2+GB of memory by the Google Play Services and is being classified as a system service.
Here is what Google has to say:
Google Security Blog Documentation
I don't want to reiterate speculations by others what this really does on your phone. Depending on the sources it is either meant for scanning content and filtering/warning users; flagging illegal content; or providing the underlying "AI" models for various other tasks including the above.
Some opinions and commentary to consider:
Graphene OS developers (Warning link to Ex-Twitter)
The Hacker News
Dedoimedo
Protectstar