"Chicken" can be the word for the birds in general. "Lots of chickens", or it can mean the adult female of the species "The chicken lays eggs". "Chicken" is also used for the meat of these birds. "Hen" is another word for the adult female, and can be used for other poultry (pheasants, peacocks etc.). The male is a "Rooster". A young male is a "Cockerel". An immature female is a "Pullet". Little yellow ones are "Chicks".
There, that's enough farm words for today....cluck, cluck, cluck....
The italian pronunciation is not correct: you have to say "póllo" with the close 'o'. You can listen to the correct pronunciation at http://www.comesipronuncia.it/pronuncia/pollo-11074