These are conditions where the brain has problems processing the information sent from the 5 different senses - they provide the brain with data giving us the ability to perceive in our world
The 5 senses are sight, hearing, taste, smell, and touch. There are other senses - there is some debate as to whether they are in fact “real” senses. These include temperature, kinaesthetic sense, pain, balance and so on.
The traditional 5 senses send data to the brain where they processed, or interpreted. When this interpretation goes wrong, or the data in not received accurately, then you have a sensory processing disorder.
In people with ADHD the involuntary reaction to sensory data reaching the brain intensifies distraction. The ADDer will automatically “go to the source” of that data.
One of the favourite tricks Occupational Therapists use when lecturing to illustrate this phenomenon is while they are busy doing something else, they will surreptiously break an ampoule containing something with a distinct odour.
The ADDers in the room will react almost immediately, they will start sniffing the air, seeking out where this unexpected smell is coming from. Of course they are no longer attending to the lecture.