Ego - Shadow self - Pain body

I have a question. How would you define what is the difference between ego, shadow self and pain body? To me it seems they over lap partially or are all active in layers. How do you recognize which one is active and how does it effect on how you approach it, or does it? Also, does all the pain we experience come through or from our pain bodies and do we experience any pain after the pain body is being dissolved? Or does it actually dissolve or do we just solve our attachments to it? Is there a difference in the pain bodies or in how they function/show up for empaths and catalysts?

I'd love to hear your thoughts about it. 

Thank you <3