The first fermentation called alcoholic starts above 16°C (60°F). Sugars are turned into alcohol while carbon dioxide and heat are released.
Alcoholic fermentation usually takes place in vats (steel or cement) where it is easy to control both temperature and speed of fermenation. An error at this stage can result in wine faults.
The pomace (skin+pips) is then pressed and mixed with the fermented must. Now can the second fermentation (malolactic) start.
Malolactic bacteria consume malic acid (naturally present in the grape) and convert it to lactic acid. MLF is essentially the conversion of malic acid into lactic acid. As a result the wines become rounder, fuller and less acidic. Practically easier to drink and to match with food.
After the two fermentations are completed, the wine is separeted from its lees (dead yeast cells) and sulfites are added to protect against oxydation. Now it´s time to sleep! Barrel fermentation, storage, and aging will cause the wine to absorb taste from the wood, like vanilla, caramel, spices, smoke and toast flavors.