What is autism

I don't come on here very much because I don't like to think about how I'm "autistic" apparently, no offence to anyone who does like to think about that but I don't.

But when I do, I can't work out what it is. I've read that it isn't a physical medical condition and it isn't a mental health problem so what exactly is it. If it's just a way of thinking that a person has then why label it other than to just call it their personality?

Another related question, I am often (as in twice in the past two weeks) in ambulances. I don't need them but if strangers see me having a seizure they panic. Medical people always want to know my other medical conditions, should I tell them autism?