The title mostly covers it, but why did some people in the concentration camps survive through the war and others did not?

I'm sure there's many factors at play, but was a young and able-bodied person kept around for labour? Was gender a factor? Were individual camp commandants more apt to kill in some camps and others less so? Was it better to enter in the late war period?

Could someone "increase" their limited odds of surviving or was it just pure chance?

Thank you! I hope I worded this question accurately, I know the Holocaust was systematic and organized, but I wasn't sure if the Nazis themselves were looking for certain factors when they assigned victims to different camps or outcomes, or if it was just indiscriminate extermination of an entire people.