Single cohort but comparing two groups WITHIN this cohort


I have a single retrospective cohort that was selected over multiple years, without a control cohort (it is not possible to find a control group in my case). However, I'm comparing the group of individuals within the cohort who had a certain event with the rest of the cohort who didnt have the event, to try and see if there are risk factors that can lead to this event.

I'm just trying to describe the this called a cohort study? Or a descriptive case series? And what would the type of analyses I do, by comparing the two groups within my ONE cohort, be called?

Thanks for helping me understand what I'm dealing with!