Malolactic fermentation is a secondary fermentation in which lactic bacteria convert tart malic acids (like what's in apples) into lactic acids (like in milk). Malolactic fermentation is well known for producing buttery characteristics in Chardonnary. In fact there were times when California winemakers went crazy with this process and produced some wines that really tasted like butter. Nowadays most winemakers have mellowed, using the technique in moderation. In fact, malolactic fermenation is used to make almost all red wine, and many whites. It takes away a bit of acidity, and can add complex notes, but it may also take away some of the refreshing crispness of a wine. This is one of the many techniques a winemaker has in the arsenal that will change the final product.