A “hen” is, of course, a female bird. A male bird is called a cock, or a cockerel. His job is to look beautiful and make lots of noise. Just like a man, in fact. Very often, people say “chickens” when they mean hens, though strictly a chicken is a baby bird. Hen meat which you buy in a supermarket is always called “chicken”. It sounds so much better than “hen meat”!
My grandmother, however, did not call her hens “hens”. She talked about her “fowl“. Fowl is an old word meaning birds which are kept or hunted for their meat or their eggs. Another word which you may hear is “poultry“. Poultry just means birds kept for their meat or their eggs. A poultry farm is a farm where they keep large numbers of birds, sometimes in big sheds, or sometimes in tiny cages called “battery cages”.
My wife and I have our very own poultry farm, only a few kilometers from the centre of Birmingham. Last summer, we bought three hens, a hen house and a little hen run. The hens grew big and fat, they wandered round our garden and they laid big, brown eggs. The hens were happy. We were happy. (Full text here)