The purpose or the topic of what you´re going to be writing.
Prospect, it means: potential things that may come to pass, often favorable, or to search for something, like gold.
An example sentence using prospect as a noun is: The result, therefore, of this physical inquiry is, that we find no vestige of a beginning,— no prospect of an end.
An example sentence using prospect as a verb is: During the gold rush in California, many people prospected for gold by panning in the river.
N. Scott Momaday
Referencing the trail he followed to understand the tales of his grandmother.
