What's really interesting bout canning is that it was the result of an X-prize set up by Napoleon who was trying to find a way to feed his army more reliably and less hardship on the local farmers then living off of the land. Armies had become too large to pull that off.
Nicolas Appert won the 12,000 franc prize with a process that not only preserved food but killed off any microorganisms that could spoil the food. That was the start of the water bath canning process. Some competitors canned their foods without the water bath part of the process and a lot of people died from food poisoning. It would be some 50 years until Louis Pasteur would figure out why and how to prevent it.
It was our sad duty not to long ago to help an elderly brother in our ward remove a lot of old home canned goods from his basement. His wife had been an avid canner, and had died a few months before; since he was going to move into a daughters home he was donating it. We did find some very old items way in the back corner that was labeled in the '70s that we just tossed but most was in surprisingly good condition.
Mostly canning is about taking the harvest from summer and fall and preserving it for the cold of winter. It also comes in handy to buy food when it is least expensive and saving it for later. It is a great frugality trick.
Canning is a lot like baking, there is relatively little room for error so following the recipe precisely is important.Now the bible of canning is the Ball Blue Book of Canning. It has been the standard for decades.