Netorare

[Sarah]

literally means cuckold and shortened as NTR is a hentai genre where in a heroine will be introduced as having a significant other, which may be a husband, a boyfriend, or even a partner in a BST affair. The story will then show the aforementioned heroine being intimate with another man thus provoking jealousy in the audience by proxy.

[Sarah]

A vastly overrated genre that has its origins with crappy shoujo anime and manga. Its basically a Japanese term for cuckolding, and only a jealous mangina would do that to another guy.
The direct opposite is called Netori where the protagonist steals the girl from another guy, however only a loser would have that happen to him anyways.
Like most shoujo manga it usually but not always involves rape, is poorly written, cliched, done mostly for shock value,and takes little talent and writing skill.
While it used to stick to mainly hentai and shoujo, there a attempts at making it main stream but it the non existent plot is painfully obvious to those who arent teenage girls or jealous old farts. Most artists and writers who use it tend in their works tend to be talentless hacks.

[Jessica]

Its a genre of adult manga or hentai. It should be defined as CHEATING/Unfaithful/Adultery.
It is too often INCORRECTLY defined as [cuckholding]. However true readers of the genre know that cuckholding is just a sub-element and a fetish. A fetish where one likes to watch their significant other, [having relations] (usually sexual) with another person.
In NTR however the the a bf/gf/wife/husband Do Not have to make a appearance in the story whatsoever. They often Do Not Ever find out about the betrayal. In some [ntr] the cheated on individual may in up in a situation where they are forced to watch there significant other cheat on them. To go slightly further. Some ntr is known as [NETORI]. This can also be defined as Cheating. Ecxept its from the point of view of the individual stealing away the heart of someone already in a relationship. Once again the gf/bf/wife/husband never has to make a appearance in this type of story.
For the illiterate/[Tldr];
[Netorare] is just Cheating NOT [Cuckholding]. The individual being cheated on may never find out or even be shown in the story.
A sub-element at best seldom/sometimes used, Cuckholding is a fetish. About an individuals desire/want to be cheated on by their significant other.