Just what is preserving, anyway?
Preserving food is a way of locking in the freshness of the ingredients, so they can be safely stored in the refrigerator, a freezer, or even on a shelf, for relatively long periods of time. That's the easiest answer.
It is so much more though. There are many methods of preserving, besides cooking up delicious concoctions and sealing them in jars. Canning is just another name for "preserving food in jars"; we haven't used actual cans for a very long time.
An assortment of preserves in 4 ounce jars
Fermenting, pickling, curing, candying, infusing, smoking, brining, freezing, and dehydrating/drying are also considered preserving, as is wine making, beer brewing, and cheesemaking. All are ways to take fresh, high quality ingredients, and using the alchemy of a kitchen, turn them into something often completely different that what we started with, and more often than not, much better!