Salt preserves foods by creating a hostile environment for certain microorganisms. Within foods, salt brine dehydrates bacterial cells, alters osmotic pressure and inhibits bacterial growth and subsequent spoilage. Salting fish made long-range explorations possible in the age of sailing ships.
Smoked foods contain polycyclic aromatic hydrocarbons which are known carcinogens. Smoked foods are known to be carcinogenic when eaten as a regular part of a person's diet. Most people do not eat enough smoked foods for this to be a major concern. HOWEVER, the hotter the wood or charcoal burns, the more polycyclic aromatic hydrocarbons that are produced.
Pickling is one of the oldest methods of preserving foods. Pickling is the preserving of food in an acid (usually vinegar), and it is this acid environment that prevents undesirable bacteria growth. However, how and what kind of acid gets into the liquid is what can cause some confusion about the use of salt.
Most pickled foods are salted or soaked in brine first to draw out moisture that would dilute the acid that is added to 'pickle' the food.
The canning process was developed to preserve food safely and for long periods of time. Once a food is packed into a can, the can is heated to a temperature extreme which kills all known microorganisms.