You will find there are many words used regarding autistic symptoms. I am going to name and try to define a few of these .
Proprioception: The way you relate to your body in space.. how you see and feel where your body is located in any given situation… you use your sense of balance, vision, depth perception, perhaps sound and sense of touch or feelings of pressure to keep yourself oriented to your place and position as you sit at your desk, lie in your bed, take a shower, participate in activities, etc. When you do these things, your system senses where you are, what physical position you are in, how fast you are going ( or if you are sitting or lying).
Praxis: The ability to move your body into various positions or motions in a direct or meaningful way. The ability to make precise muscle movements to perform various tasks… the ability to rise from sitting, feed oneself using spoon or fork, to form words with tongue and lips in order to speak, etc all involve deliberate movement to perform certain tasks. Apraxia or dyspraxia describe the lack of precise ability of praxis. Uncoordination of movement or speech impediments would be examples of this.
Vestibular: Related to the inner ear system which directs balance and sense of movement, feelings of motion… many autistic people seem to seek to stimulate the vestibular system through self comforting behaviors such as rocking, spinning, swaying, nodding, etc.
Stimming: Self stimulating behavior which seems to release tension or comfort an autistic person. Anything can be a ‘stim’ … stereotypical behaviors include the above mentioned motions of spinning, rocking, swaying, nodding… can also be foot or hand motions, humming, singing, repeating word or songs over an over, also such things as self grooming, twirling hair, sucking thumb or fingers, constantly chewing gum, or other things. repeatedly performing almost any behavior. These or any actions done as a form of release or self comfort are called self stimulation, or stimming/ stims.
Not all autistic people have stims, but many of us do. Many stims are not as obvious as classical hand flapping and rocking… Some of us have learned to redirect things such as hand flapping into sitting on ones hands or holding onto them, perhaps we take up running or walking, swimming, or eat constantly instead of the more obvious stims from our early childhood. I was stunned to realize I had many stims in childhood and have redirected them as I am now a mature adult. But I still have them!
It is a false assumption that all autistic people participate in self stimulating behaviors.
It is a false assumption that stims are fixed behavior and do not change.
Sensory processing : The neurological ways we deal with any input to our senses. Many autistic folk process sensory input in different ways from what is considered the norm (neurotypical). Although it has been common in the past to say that autism is essentially a neurological processing disorder, now it is more politic to say it is a less common form of sensory processing.
Many autistic people will say it is not a disorder at all, comparing it to the differences in computer operating systems, Mac and Windows for example.
I will not get into the politics here, but will stick to the definition of sensory processing as simply whatever way any given individual receives sensory input and translates it to useful information within any given neurological processing system.