what is digestive system?

I would suggest that an easy reply would be something like the following:............The digestive system consists of various organs which work together to to break down and / or digest food that is eaten, so that it can be absorbed into the bloodstream.The bloodstream then carries the broken down food to the body's cells, which uses it for energy, growth and repair damaged tissue.

This website describes the digestive system: http://en.wikipedia.org/wiki/The_Digestive_System An easy answer would perhaps be "The digestive system helps break down food, absorbing nutrients the body needs and passing out those that the body does not."