Sterling is the world's oldest currency that is still in use. This is used in the 9 associated territories.
The pound tends to refer the British currency only. It is often denoted as the British pound or pound sterling.
At present, the sterling is the worst 4th most traded currency after the USD, EUR, and JPY. Together with those three currencies and Renminbi, it forms the basket of currencies which calculate the value of IMF special drawing rights.
The Bank of England is the central bank that creates the monetary policy related to the pound sterling. It issues its own banknotes and regulating issuance of banknotes by private banks in Scotland and Northern Ireland.