Answer: The word "plot" relates to several things. The argument of a story, a plan, a conspiration. What this things have in common is that something is hidden. There is a mistery behind those things, something to be revealed or to discover, bring to light. Something to hide, to conceal from the reader, another person, etc.
It is important due to the fact that those two factors have a significant influence on that person's current mental state. When trying to help someone, you are attempting to see the root of their conflict. Cultural and Social factors may be the root.