Don't feel bad. We all went through that stage!
I was fortunate to have spent years around nursing terminology, so... was familiar with diagnosis, rx, therapist, psychiatrist, etc.
But difficult child? Nope. Someone asked before I did, so I learned that way, but...
Yes, its confusing.
Almost as confusing as going onto a website for some technical area - civil engineering, or information technology - if it isn't your own field of work... What is a TDD? (no its not a telephone device for the deaf - at least, not in MY industry)!
But like anything else, come play along and before you know it you'll be telling us about your difficult child's latest diagnosis, or rx change, or problems with the therapist... just like the rest of us!