An outline reduces a to

sentence . . a word
metropolitan area . . a small city
large amount of information . . the essentials
huge number of documents . . the main paragraphs

An outline reduces a large amount of information to the essentials.

An outline refers to the description of something by presenting the important information about it and not the detail.

It helps in presenting ideas about a thesis or topic in a logical manner. In other words, it refers to giving rough sketch or summary of something.

For example:

The teacher gave the outline of the story "The Letter."

i'm sorry i don't understand the question.

often a noun phrase is just a noun or a pronoun:

people like to have money.

i am tired.

it is getting late.