The process of preserving food by fermenting it in brine is called pickling.
In fermentation pickling, vegetables or other foods are submerged in salty brine under low-oxygen conditions. Lactic-acid bacteria, especially species in the Lactobacillus group, consume available carbohydrates and produce lactic acid. The rising acidity suppresses many spoilage organisms while creating the sharp, complex flavor associated with fermented pickles.
Pickling is broader than fermentation alone. Foods can also be preserved by immersion in vinegar, a method often called chemical or quick pickling. Salt concentration, temperature, oxygen exclusion, and fermentation time all influence which microorganisms dominate and how crisp, sour, or aromatic the finished food becomes.
Sauerkraut, kimchi, and traditionally fermented cucumbers are familiar examples. Pickling is not the same as curing, which usually relies on salt, sugar, nitrates, or drying to preserve meat or fish; smoking uses smoke compounds and dehydration; and canning relies on heat treatment and sealed containers. The English word “pickle” traces back through Middle English to terms associated with brine.