Stimming stands for “Self Stimulating behaviour”. This behaviour may occur when individuals with Autism are confronted to stressfull situations or sensory overloads, they are a way to cope with what is going on.
Examples of stimming are: Flapping with the hands, Fidgeting, Chewing on objects, …
This is normal behaviour that usually means the person is able to cope with the situation. Sometimes they do it without realising it, as it is some form of instinct to calm themselves down.
A form of stress
I think stimming is a form of stress, when people see me doing it they might ask why I’m stressed. And considering My social anxieties and the sensory overload that usually goes with the stimming, it might be true. Stress is actually a warning mechanism of the brain, and it is proven that doing things like chewing (this includes chewing objects) reduces the stress.
To many people without Autism it might be wired, but for many on the spectrum it is normal. It makes us feel comfortable, after all, you should feel conformable everywhere you go, otherwise something is wrong.