Dinner has been known (in many western cultures) as the largest most formal meal of the day. It is also a meal that is most often eaten during the evening but has been seen to also be a meal that you can eat in the afternoon. Many times these are the meals that we have a lot of family over for when there is a special occasion.
Now there can be many different words for dinner. A popular one is supper referring to a secondary evening meal. Many people make entire events out of this meal in creating, dinner parties.
When its the holidays I always look forward to special dinner items, such as having Turkey on Thanksgiving or Corned Beef on St. Patricks Day. Its really a meal that can be so universal and have many people having the same thing on the same days.