There are a few agencies that ask for them but most people have nothing worth writing about - I certainly don't and for that reason tend to avoid submitting to such places
However, you're right it's not like a CV listing your qualifications and work experience, but more of a character sketch and any writing credits and any CW courses you've been on. If you don't have the latter, then maybe just give them a character sketch of yourself.
<Added>PS. Good luck with the submission!
<Added>Oh, and one photo, unless they've specified a number.