A natural wine is produced from grapes farmed organically or biodynamically.
The main differences occur in the cellar. No additives or processing aids are used, and ‘intervention’ in the naturally occurring fermentation process is kept to a minimum. Neither fining nor (tight) filtration is used, and at the end of the wine making process, no sulphur is added when bottling the wine.
Nearly always natural sparkling wines are of the cloudy Pet - Nat style (have a look to ancestral method here).