NTR is an abbreviation for “Netorare,” a term derived from Japanese anime and manga. It refers to a specific genre of adult content that centers around infidelity and betrayal, often involving a romantic partner who is taken away or seduced by another character.
NTR also has subcategories.
Netori, unlike Netorare, you steal someone else's partner.
And.
Netorase, the partner is shared. Usually there is dubious consent.
And BSS, (But I liked her first). There is no offical relationship between the characters. Other then having a crush. And another character "steals" the crush.