'assistants' vs 'assistant_output' difference for file upload purpose?

According to here, a file purpose can be ‘assistants’ or ‘assistants_output’
What is the difference? Can I specify either of these two on upload?
When should I use which value?

I could not find this anywhere else in the documentation…


Good question, I am looking for an explaination too.

I am also looking for an answer to this question as well, thanks.