<unk>  is a method of preserving food where the food is sealed in an airtight container. It prevents microorganisms from entering and proliferating inside.
To prevent the food from being spoiled before and during containment, quite a number of methods are used: pasteurization, boiling, other means of high temperature applied over a period of time, refrigeration, outright freezing, drying, vacuum treatment, antimicrobial agents that are natural to the indegenous recipe of the foodstuff being preserved, or otherwise are applied to the contents of the can, a sufficient dose of ionizing radiation, submersion in a strongly saline, acid, base, osmotically extreme (e.g. very sugary) or otherwise microbially challenging environments.
No such countermeasure is perfectly dependable as a preservative. E.g. spore-forming thermo-resistant microorganisms, such as Clostridium botulinum (the causative agent of botulism) can still survive.
From a public safety point of view, foods with low acidity, i.e. pH more than 4.6 need sterilization under high temperature (116-130°C). Foods that must be pressure canned include most vegetables, meats, seafood, poultry, and dairy products. The only foods that may be safely canned in an ordinary boiling water bath are highly acidic ones with a pH below 4.6, such as fruits, pickled vegetables, or other foods to which acidic additives have been added.
Canning
Bedwetting
Polishing 
Burial
Dosing
Mourning
Concoction
Gaslighting