Pickling is the process of preserving food in brine or vinegar. While "pickles" in North America refers to pickled cucumbers, it is common to pickle meat (such as pig's knuckles), fish (herring), fruit (plum) and other vegetables (green bean, radish, etc.).
The pickling process is fairly simple but requires a bit of time. First, the container, usually a jar with lid, is sterilized. The food to be pickled is placed in the jar, and the jar is filled with vinegar or brine. Spices are added as desired. The container is sealed and heated in boiling water, then left to sit for several weeks.