Pickling is a method of food preservation that used to be far more common. Fruits, vegetables, and meat are pickled by submerging them in brine (a saltwater solution). This allows them to ferment; the growth of good bacteria is encouraged and the growth of bad bacteria is inhibited. The amazing thing about pickling is the way that it enhances the flavor of a particular food; some foods just taste better pickled!
See 11 Delicious Things You Didn't Know You Could Pickle here: http://www.thedailymeal.com/11-delicious-things-you-didn-t-know-you-could-pickle