Well, the United Kingdom is NOT England, but it englobes it. It is a common mistake !
The UK is divided into 4 distinctive parts :
England (its capital is London, of course !)
Scotland (its capital is ... Edinburgh, and NOT Glasgow)
Wales (Cardiff is the capital, what type of sport is famous there, do you know ? Rugby ? Well done !)
Northern Ireland (its capital is Belfast) ; the History of ireland is a complicated one. See the corresponding file for more details.