Just like a woman - the egg (ovum) is released from the ovary and travels through the fallopian tubes. In a woman, if it's fertilized, it implants in the uterus. If not, the egg continues and is flushed out monthly during the woman's period, along with the blood-lining of the uterus. In a chicken, a yolk and whites and shell are built around it. If it's fertilized and kept warm, etc, a chick grows inside until it's ready to hatch; otherwise, the egg comes out anyways, just not fertilized. In a woman, it's about a 28 day cycle. In a chicken, it's about a 25 hour cycle.
Does that help?