It's in the other types of communication you might do without being aware of it. Different people have different ability when it comes to this sort of thing. Some might be very good at picking up on it. Others might be terrible.
The most common way, as I understand it, is to read your body language and facial expressions. Alot about you, how you're feeling, what you're thinking, these things are shown in those aspects. While many on the spectrum cant process this aspect, most NTs can.
Another is your voice. I dont really hear people talk about this one much. This is the one I'm good at. If you were to talk to me, vocally, I can read everything in your voice that isnt the actual words you're using. I know how you're feeling, I know what you're thinking, often I even know what you're about to do or say. No, I dont know how I do this. I suspect that is the same with those that read body language. They dont really know HOW it works... it just does. Sometimes, things are like that. They simply are.
As such, dont expect a hugely detailed explanation of these things. There's all sorts of theories and such related to how the brain processes this stuff, but really, it varies wildly from one person to the next.
One way or another though, I tell you this: try to have confidence in yourself. Stop thinking of yourself as weak. If you change the way you're thinking, people will naturally stop picking on you. This is a lesson I learned the hard way. Was bullied endlessly through my school years. These days though, most people simply avoid me or get out of my way, despite that I'm as physically imposing as a flower. That's just how strong these non-vocal forms of communication can be... it has a very strong effect on whoever is receiving it.
So yeah... think positive. The better your attitude and confidence, the less often you'll have that trouble.
Hope some of that helped instead of just making it more confusing.
