do the chickens lay eggs? or are they just for selling?

[Giddian]

after you sell them all, they are gone forever?

[American Dove Mitten]

Ops sorry, I read the question wrong. Yes, they make eggs overnight. You can pick them up with the basket at the chicken house.

You can’t Breed chicken as far as I know. But you can buy more from the mail dude.

[ElusiveOne]

Be sure to pick up eggs every day because they won't lay more if there's already some in the hen house. You can eat or sell them. Since there's 6 every day by default, I usually sell most of them to the postman and keep 1 to eat.

[Grintus]

I would add something to this topic, as even knowing that there are eggs, I searched myself stupid where I can find them, or trying to get into the chicken house. I really had no clue about this.
Solution: You have to pick up the basket and THEN click the chicken house to collect the eggs!