Supper depends on where you are from. I've heard of it as a later, light dinner but also as an synonym for dinner for the posher/aspiring Brits, and Australians, while a dinner for the British working man was supper (vs. high tea). Term originates from the French word souper which is the evening meal, usually served with or featuring/highlighting a soup. The contemporary terms for the main meals in France (petit dejeuner, dejeuner and diner) supposedly originate from the aftermath of the French revolution where there was hunger due to collapse of food production (and distribution?) so there were only two meal pushed later and apart. In French-speaking places that predate the French revolution and were not touched by so (e.g., Belgium, Switzerland, Quebec). dejeuner, diner and souper are used.