Generally speaking, natural wines are made with minimal intervention in the winemaking process and no chemicals. When chemicals (herbicides and pesticides) were not yet invented, and when refrigeration was not yet invented, winemakers made natural wine, meaning Mother Nature dictated the qualities of the resulting wine and the winemaker mostly went along for the ride. It was just fermented grape juice then, not altogether an inaccurate definition of natural wine today.
Natural wines can also be called "low intervention," "zero-zero," "naked" or "raw" wines. I prefer "low intervention" wines as the easier explanation compared to something sounding like a reality TV survival show.
A winemaker might also describe his or her winemaking philosophy as "hands off" and "minimal intervention".
Natural wines have no regulatory definitions, yet. "Natural" does not appear on the labels, however most natural wines are made with organically or bio-dynamically farmed grapes. The practice includes only wild or native yeasts to trigger fermentation, no added flavor enhancers, limited filtration, limited fining agents and minimal or no sulfites added as a preservative. It's the winemakers discretion to use all or some of this methodology. Because it speaks of a healthy lifestyle and an eco-friendly environment, natural wines are here to stay and business is semi-booming. (Extraordinarily big booming in large metro markets).
Does this mean healthier wines to drink? Yes, of course it does, and the unofficial commentary is people are unofficially feeling better and more importantly, unofficially getting less headaches, especially with red wine.
There is a curve: Natural wines can taste interestingly different, so don't give up on your first try. White wines can be cloudy...not a problem? Red wines can have sediment...not a problem? I like to recommend natural wines from France and Spain and people are indicating feeling better with wine from these regions.
Try this: Google the winery and the "winemakers notes" on what you are drinking. You will be amazed how many wines are following these "natural" practices, and have been for many years. It's difficult to find another industry taking better care of their natural resources than todays wineries and passionate winemakers.
Cheers!