Things like trays of chili or beef stew or macaroni and cheese.
Why no refrigeration needed?
Are they filled with salt? Irradiated? Parboiled?
Usually, they’re heated within the package to temperatures high enough to kill all the nasties. Radiation has the same benefits, with less effect on the quality of the food, but it’s unpopular due to the general American fear of all things radiation. But it is sometimes used anyway: I have some packets of red pepper from Papa John’s that say they were radiation-treated.
There will often be some sort of indication on the packaging how something was stabilized. UHT (ultra high temperature) is the term usually used for the heat method.
Another way common here is food that has been pasteurized, then packed at heat in pure nitrogen. Inert, natural in air, but bacteria can’t grow. Very clever way of packing food I think.
It is the packaging, called a retortable pouch. The food is processed just like it is for packing in tin cans. After the pouch is sealed, there is no bacteria inside to cause spoiling.
Ultra High Temperature (UHT) pasteurization.
It will also work on other liquids, and there are patents out to use it on raw meats.