Hens and frogs both of them are egg layers. But the main difference lies in where the fertilisation takes place.
In hens, the fertilisation of it's egg occurs inside the body where as in frogs, the fertilisation of eggs happen on the water that is, it is external. Again a hen's egg has a hard shell whereas the egg of a frog does not have a hard calcareous shell ,instead it is protected by a soft jelly like substance.