A parton fragmentation function can be interpreted as the probability that a final state hadron originated from that particular hadron.
A parton distribution function can be interpreted as the probability some parton with momentum $xP$ ($x \in (0, 1)$ and $P$ is the hadron momentum) lies within that hadron.
So what exactly is the physical interpretation of a hadron distribution amplitude. I know it is related to exclusive processes. But how would I go about explaining what a hadron distribution amplitude is to a 5-year-old (or me for that matter)?
