I examined my options. I could tell her that I know about autism because of my sister being Autistic. But that would be wholeheartedly untrue - autism understanding isn't the kind of thing you pick up by osmosis, and pre-website making I knew next to nothing about autism despite having a sister on the spectrum. I could also say I know about autism from caring for kids on the spectrum. But being a caregiver teaches you how being autistic affects that one child, not all autistic people.
One by one I went through and discarded each possibility, and finally, hours later (after I'd mumbled something about not having professional training), I found my answer.
I know about autism because I listen to autistic people.
That's it. There are no special requirements for this understanding - you don't have to be born into a certain family or pay for certain classes to earn it. That understanding is there for the taking for anyone who wants it. And, yet, it is utterly rare.
One of the many barriers that keeps people from this knowledge is not knowing where to find it. But you don't have to know an autistic adult in person to learn - there are so many collections of their writings and meeting places online. Check out Autistikids, a website which brings together the descriptions of people all over the spectrum of what it's like to be autistic. Or go through WrongPlanet, the discussion forum for people on the spectrum and read as they describe their lives and what's important to them, and ask questions when you want to learn more.
There are so many paths to this understanding, and they're all free for the taking. For those of you new to this journey, please join me on one of these paths. You have nothing to lose and there is so very much to be gained.