Why do we need `curveid` argument of the `drm()` function?

[greenjune-ship-it]

Dear Team,

I have a question regarding curveid parameter of the drm() function.
In which cases do we have to use this argument? Should it be distinct groups like different species or different treatments/conditions or should it be more or less similar groups like biological replicates/different individuals?

The existing documentation is not clear enough, so any comments from you will be really valuable.
Thank you in advance!

Best regards,
Yulia