The Hentai category, this would refer to the female on female section of it, or in more Western Civilization terms, the Lesbian section.
Also referred to as Girl Love, or wasi-eigo, this is akin to Yaoi..
The romantic aspect, has been noted as being called shojo-ai, but mainly in Western Civilizations.
This is due to the Japanese form, having a negative connotation.
Yuri is the original or parody works, found in Anime, Manga, and such, as Yaoi is.
Features can be exaggerated, or made more sexual in depiction, than in reality.
Yuri can focus on either the sexual or emotional aspects unlike Yaoi.
While rooted in the Lesbian movement of the early 20th century, it wasn't until the 1970's that it began appearing in Manga.
The 1990's some changes, and the first Yuri Manga magazine wasn't launched until 2003.
The word itself, literally means 'lily' and is attributed to being used in a magazine, in 1976, that was predominately for gays.
Those in the self published circles, began to use the term, Yuri, to denote Hentai material, that dealt primarily with the attraction, sexuality of two females.
The terms Girls Love is mainly used by publishers of this genre, while most authors, fans, rely on the term Yuri.
In Japan, the term can refer to either sexually explicit, or non sexual, attractions of two females.
Western Civilization, however, seem to equate Yuri with more lurid, sexually explicit content, than their Japanese counterparts.
Practice (Associated Acts):
In its beginnings, the story line generally involved an older, more assured woman in the lead, coupled with a much younger partner, less sure of themselves.
Many of the relationships were romantic in scope, but plutonic.
Early on, the central theme was around older, but only slightly, women with slightly younger females.
Later it transitioned to where the older female, was considerably older, more sophisticated, while the other partner, was much younger, less worldly.
This usually involved a high school or freshman female, in the younger role.
However, earlier renditions usually included the older person dying at the end, from various means.
Not until the late 1990's did that standard plot line begin to soften, to change.
Many of the themes dealt with school girl crushes, with family issues, between the two women.
Western fans coined the term Shojo-ai, similar to the term Shonen-ai for men on men, involved in a more romantic depiction, than sexually explicit.
However in Japan, the term has a highly negative implication, more in tune with pedophilia,
The first magazines, dedicated to Yuri themed works, appeared early in the 2000's.
It was at this point, that the central theme began to explore more general Lesbian themes, more realistic and modern.