
On the terms "Yuri" "Shoujo Ai" "GL" and "Lezu"
Yuri describes intense emotional relationships. It is about LOVE, and not sex. Always has been, because it was created by and for lesbians as a way of expressing themselves. It evolved out of the Class-S genre which was about intense but temporary relationships between girls in school.
I don't know where the western anime fandom got it into its head that "Yuri" has anything to do with porn or other erotic content. Yuri can have erotic aspects, but it is primarily a romantic genre. As such, the term "Shoujo Ai" is extra idiotic because not only is it something that non-japanese speakers made up; It is also a term that was made up to describe what "Yuri" already describes.
"Girls Love" or "GL" are not just terms used in the west. In fact, I'm pretty sure the Japanese invented them. GL is very similar to Yuri; They aren't exactly the same, but there's a lot of overlap.
"Yuri hentai" is almost a contradiction in terms, to the point where the japanese tag for it on DL site is "Lezu/Onnadoushi" which means "Lesbian/WomanOnWoman." The tag for Yuri also does exist, but it is exclusively used for works that contain a strong emotional connection. "Lezu" is also not a term you want to throw around because it's extremely vulgar. "Yuri," on the other hand, is completely respectable.
In fact, Yuri is so respectable (Because of its proximity to Class S) that the amount of lesbian subtext you can sneak into a show for little girls is functionally limitless. For example, the writers of the pretty series, which is a commercial for an arcade game, went completely mad with power somewhere around Season 2 of Pripara.
The image I used for this post is from episode SIX of the FIRST season of Himitsu Aipri, and an actual "Isn't the moon beautiful" between the two of them in the second season, which is like confessing love by quoting Shakespeare.
That, and they also just say they love each other about thirty times an episode.
I could say more, but this post is long enough already.