...Spider-Gwen? Is it set in an alternate universe, or something?
Yeah. Zygarde already mentioned the basic concept:
Also yeah that's real I believe that other Spider person is an alternate reality Gwen Stacy where she becomes Spider-Woman.
So right now Marvel has two Spider-Men (Peter Parker and Miles Morales, who has relocated to the main universe since Secret Wars destroyed the Ultimate Universe), two Spider-Women (Jessica Drew, the original, and the alternate universe "Spider-Gwen"). And Silk, who's a woman who got spider powers at the same time as Peter, but wasn't created until recently.