What is the difference between soup spoon and dinner spoon?

And what please? Are you asking about dinner spoon vs a desert spoon?

A dessert spoon would be the largest and placed at the top of your plate with the bowl end of the spoon facing to the left and the dessert fork placed above it facing to the right.

The dinner spoon would be to the side of the plate.

If you let me know how many courses and what type of servings you will be offering and whether it's a luncheon or dinner, I'd be pleased to provide you with a complete diagram of a table setting for formal environments, based on British style.

If you prefer resolutely american style I can offer you a Tiffany & Co outline. Or if less ambitious there's always the Arkansas setting which consists of a low trough and a shovel!