What is Photo Agent?

Hello there Mac Gurus,

I just ran the latest update to El Capitan vers. 10.11.5 (15F34) last night. So today there was a session open all day called Photo Agent—just a black screen. I couldn't figure out how to close it until just now—accidentally. Now I'm wondering if it was supposed to be open for some reason?

What is it and does it need to be open?

Thanks for any information about this that you can bestow upon me! ~Pam