Natural wines are at the zenith of pure wine making. It is both extremely risky for the producer and enormously satisfying when everything goes well! Definitions vary from country to country, but the essence is this.
Whilst no official body exists to control exactly what constitutes a natural wine, each country or grower or group of growers has their own charter, which is usually much stricter than any Organic or Biodynamic regulations.
The basic principles of producing a natural wine is that either Organically or Biodynamically Vitified grapes must be used.
The vinification must add nor subtract anything in the production process in the cellar. No additives or processing aids permitted. Adjustments to the fermentation process kept to a minimum. Finally, no filtration or fining before bottling.
So, in effect the result is a living wine. A microcosm of the terroir expressed in liquid form, naturally. The longevity of such wines is drastically reduced so they tend to be drunk young.
To produce natural wine, it has to be a philosophy and way of life. Producers are always one step away from a force of nature taking their entire crop or an issue such as re-fermentation in bottle or Vat can destroy a years work.