2019 years have humans been on earth
DNA is the genetic composition of the cells in the human body, think of it as the coding for a computer but for cells. These carry your genetic composition (blue eyes, Brown hair, tall, short blah blah blah) and traits like smart, funny, shy.
Hope that helps.
A sex cell that hasn't been fertilized and has left the ovary would come out during the menstrual cycle under normal circumstances.