Who was the mother of Queen Elizabeth II?

Elizabeth II's mother was the queen consort (wife) of George VI. She was also called Elizabeth. Before her marriage, she was known as Lady Elizabeth Bowes-Lyon. When her husband became King she received the title of Queen Elizabeth, but she was not the monarch, so she had no regnal number.

After the death of King George VI she was called 'Queen Elizabeth the Queen Mother' in order to avoid confusion with her daughter.