vs
QUICK ANSWER
"Narrativa" is a form of "narrativa", a noun which is often translated as "narrative". "Narratario" is a noun which is often translated as "narratee". Learn more about the difference between "narrativa" and "narratario" below.
la narrativa(
nah
-
rrah
-
tee
-
bah
)A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
a. narrative 
La obra tiene un estilo narrativo ágil, ya que no hay párrafos densos.The work has a quick-reading narrative style, since there are no dense paragraphs.
2. (literature)
a. fiction 
La narrativa de Cervantes se estudia en todos los cursos de literatura española.Cervantes' fiction is studied in every Spanish literature course.
el narratario(
nah
-
rrah
-
tah
-
ryoh
)A masculine noun is used with masculine articles and adjectives (e.g., el hombre guapo, el sol amarillo).
1. (literature)
a. narratee 
La historia comienza con la descripción del narratario.The story begins with a description of the narratee.