Organic foods are crops/products that are grown unprocessed, without the use of pesticides, fertilizers, or harmful additives which aid in the preservation process of most consumer goods.
All-natural, whole foods, or animal products not infested with antibiotics and hormones to meet FDA regulations.
Most grocery stores have an organic foods section tucked away in between the cereal isle and the produce isle. They are a tad more expensive than your run-of-the-mill groceries.
I'm guessing since your doctor suggested organic foods, then you are in a the midst of a miniscule health crisis. Supplement with good water intake, a multi-vitamin and correct portions.
Best of luck to ya.