Difference between an egg cell and an egg laid by a hen..
A fertilized egg is … fertilized.
The “table” egg (you but at the grocery store to eat) is not fertilized. That’s it… in an eggshell… literally.
It’s like a human woman has a menstrual cycle every month, because one of her “eggs” ripens, but she does not get pregnant every month because not every one of her eggs comes in contact with a sperm, which fertilized it.
When it (her “egg” or “ovum”) is not fertilized, she has a menstrual cycle and the lining of her uterus sloughs off as her menstruation (cycle), monthly.
(Chickens have LOTS more eggs than that!!)
Not every egg a chicken (or other birds) lay is fertilized.