Turmeric is a relative of the ginger family. It is a rhizome, which means it is tuberous and one harvests the root for both culinary and medicinal purposes. The color is a very vibrant yellow-orange, and the active ingredient "curcumin" is a natural anti-inflamatory and valued as a medicinal in many cultures.
In cooking, turmeric adds bright color to foods, and provides an earthy flavor. It is valued as an ingredient in curries, spanish rice, and in many other dishes. It is also the prime coloring agent in yellow prepared mustard, since the mustard seed itself is not that bright of a color when mixed with other ingredients.
Use turmeric as needed in both cooking and in good health. You won't regret it.