An organ is a collection of tissues working together as a unit. An organ system is a collection of organs performing a common function and working as a unit.
A body system consists of many organs, for example the digestive system contains the stomach, liver, kidneys, gall bladder, pancreas, small and large intestines.
cells are the smallest unit of life...organs are the parts of your body...and organ systems are organs working together to form systems like the digestive system...