I have had to help my 14 year old with this issue and explaining it to her friends and teachers at school. Basically your pain centers in your brain do not know how to shut off. They do not understand that you do not have a visible "injury" but your brain is telling your nerves that you do, therefore it affects your ability to control the muscles in your body (walking, talking, using your arm) since all muscles are controlled by nerves. Your brain and nerves continue to think you have an injury and way down at the cellular level they are working as if you do, releasing chemicals that cause pain, and also not allowing your pain pathways to shut off.
I hope this helps. I know it has for my daughter, and it has helped others understand how complex our brain really is! GOOD LUCK.

When I have to explain I say I have a neurological disorder and give the name of it. I keep it short and tell them it causes pain and effects my mobility. To be honest though other than because of the lack of awareness, I don't see why someone 'different' should feel they have to explain. People are nosy and think it ok to ask what's 'wrong' with people like us, but they wouldn't dream of intruding on other people's personal business. I don't personally like the great big long "Understand me" type posts that you see for many chronic illnesses. To me they seem almost combative and selfpitying. That's not to say others shouldn't use them, I just personally switch off to that kind of thing and if I do I can't expect others not to. I keep it short, simple, polite and not woe is me as I don't like a fuss or for other's to think I'm after pity. I'd like more people to know about CRPS but at the same time I'd like to think that by keeping it fairly open/positive they might go off and look it up.