Pressure cookers look like other kitchen pots, except their lids are a bit more elaborate. How they work is that they completely seal the pot. When the liquid inside boils, it is trapped inside the pot. Having nowhere else to go, steam builds up pressure. This results in higher cooking temperatures and shorter cooking times.
The pressure of the trapped steam can be measured in pound of force per square inch or PSI. You will often find this term in pressure cooking recipes. It refers to how many pounds of pressure per square inch you will be cooking with. Don't worry if this sounds very technical. The instructions that came with your pressure cooker will tell you how to read the PSI.
The gasket or rubber ring is another important component of today's pressure cookers, as this makes a seal that traps in steam and heat and allows pressure to build. The gasket fits on the side part of the cover. In order to make sure you get a good seal, make sure all the components are clean and free from food particles.
Even in the old days, most pressure cooker disasters could usually be attributed to user error, much like my mother and the beans. Nonetheless, today's pressure cookers offer a much higher safety level than their predecessors. For one thing, you can't open them until the pressure is hrefeased to 0 PSI.
Today's pressure cookers have at least three valves for safety and will automatically hrefease pressure should it build too high. Different types of pressure cookers have different styles of valves (refer to the instructions that came with yours), but if you hear hissing or noise coming from the cooker, it's the valve telling you to check the pressure.