‘Dinner’ is ‘a formal meal with several courses’ and is generally eaten in the evening. A banquet given in honour of a person or an event is also called dinner.
‘Supper’ is what we eat everyday in the evening. It is ‘less substantial and less formal than dinner’. ‘Supper’ is the last meal of every day and it is usually right. 
Note: The words ‘dinner’, ‘lunch’, ‘supper’ and ‘break-fast’ are generally used without the articles.