What Does it Mean to Pickle Something?

What is pickling? I'm sure at one point or another you've run into the term pickled onion or egg, and everyone knows that Peter Piper picked a peck of pickled peppers, but what does it mean for something to be pickled?

Pickling is the process of storing a food item in a jar of either salt and water (called brine) or vinegar. After this process is completed the resulting item is "pickled." As an added benefit, the food is also protected from bacteria because the acid solution that develops in the jar is acidic enough to kill it, allowing the food to last much longer than its average shelf life. The pickling process will also give the food a sour or salty taste; it can be done on any food item, from vegetables to fish to various meats.

Even though anything can be pickled, we only refer to one item as a pickle: the pickled cucumber, a favorite item enjoyed by many every day.