Dinner is the meal you eat at the end of the day, usually at around 5 or 6 o'clock. Dinner can be anything, but is usually some kind of meat and some vegetables.
Once means at one time in the past, for example "I had dinner there once".
It might also mean any period of time in the past, for example "I was once the owner of that house".
It might also mean as soon as, for example "Once you have finished dinner, you can go play".
To dine simply means to eat your main meal of the day, usually dinner.
It is most often used when you are talking about eating out at a restaurant.
A banquet is a very large formal dinner, usually with several courses, that is served to a large number of people at once. A less formal large dinner for many people is called a feast.