Characterization is broadly used throughout the English novel, as it is in all novels, simply by virtue of the function is serves to the plot. First, a novel is...
...a lengthy fictitious prose narrative.
A story line is the chronology of a story, however the plot is what carries all the other aspects of the story along. It is...
...the arrangement of events to achieve an intended effect consisting of a series of carefully devised and interrelated actions that progresses through a struggle of opposing forces, called conflict, to a climax and a denouement.
So the plot carries with it the conflict or conflicts, following a rising action to the point of greatest intensity (or the turning point), referred to as the climax, and ends with the resolution or denouement, where loose ends are tied off, questions are answered, and the reader is generally given closure.
The novel, as said, is fictitious, so the author's intent is to grab the reader's interest, revolving around the characters and their actions (and interactions); and the manner in which each member of this "cast" is portrayed (the characterization) is used to involve the reader, share the theme or themes the author is trying to portray to the reader, and create a reaction on the reader's part: humor, concern, displeasure, etc. The more the reader is involved emotionally, the more successful the author is in sharing his or her tale.
Characterization is not simply a question of describing a character—"creating an image." It is much more sophisticated than that; it...
...generates plot and is revealed by actions, speech, thoughts, physical appearance, and the other characters’ thoughts or words about him.
Direct characterization is when information about a character is shared in an outright manner by the author (or narrator) and even other characters. Inference is not necessary. In indirect characterization, inferences are drawn by what the character does:
...traits are revealed by action and speech.
Darcy in Jane Austen's Pride and Prejudice proves himself more worthy than Elizabeth every credited him as being. He quietly pays for Elizabeth's sister Lydia and the scoundrel Wickham to marry, to save Lydia's reputation. This is indirect characterization.
In Austen's Emma, Emma admits that she has been ridiculous:
"I am perfectly satisfied," replied Emma, with the brightest smiles, "and most sincerely wish them happy."
"You are materially changed since we talked on this subject before."
"I hope so -- for at that time I was a fool."
This is direct characterization.
Characterization affects the English novel, and all novels, by providing information regarding the characters that supports the story's plot.