The difference is partially geographical usage. Northerners eat breakfast, lunch and dinner. In my area of the South we eat breakfast, dinner and supper. Historically, our main meal was at mid-day.

They're both wrong. 1. have supper 2. have dinner The difference is regional.

It's a long time since I've heard anyone say 'supper'. We always say dinner.

I would say that in the UK there is very little real difference anymore between saying "supper" or "dinner". I certainly wouldn't notice!

In the UK this is a geographical as well as a class question. It's too complicated though to explain fully, so I won't try. You should note however that we don't use the article. We simply say "have dinner" or "have supper".