What is the difference between the organs of digestion and the accessory organs?

Organs of digestion directly digest food while accessory organs don't.

The organs of digestion are practically one long tube throughout your body and they directly digest food by churning it (the stomach) and getting out important minerals and water (small and large intestine.) Accessory organs aid in digestion by secreting enzymes and other processes, they never physically digest food but they help the body to do so. An example of accessory organs would be the gallbladder, pancreas, liver and salivary glands.