Total noob question but how exactly does bara differ from yaoi? Not just definition wise b...

I'm no expert, so this is just how I distinguish them (we need some "definitions" for that).
Basically yaoi is made by women for women/girls and bara's target are mostly homosexual men.
Yaoi tends to focus more on the relationship and feelings, while bara is more like pornography (?). I haven't read many bara manga so I'm not sure, but I remember reading Gengoroh Tagame's works and wasn't very impressed. I mean the art was good, but if I want gay porn I can just watch it ╮(￣▽￣)╭ I'm probably being totally ignorant... But I've read that bara is more realistic (e.g. sex scenes, gay life) while we all well know yaoi is a girl's fantasy ^^
As for art: yaoi characters are more beautiful, feminine, delicate; bara characters are usually muscular and manly, can have facial hair, hairy legs etc. and bara don't really distinguish between a uke and a seme.
There's also a so-called subgenre of yaoi manga: gachi muchi (this is what we here call bara, but it's not exactly correct) with muscular, big, hairy men, but it's still mainly created by women.
This is bara: http://myreadingmanga.info/gengoroh-tagame-training-camp-eng/
This is gachi muchi IMO http://www.mangago.me/read-manga/terpenoid/

This is just my interpretation, but as I said I'm no expert...

actually, bara is gay manga targeted for men. that is why they don't really distinguish between seme and uke.

while yaoi is basically gay erotica targeted for women (while shounen-ai is gay manga that focuses on romance and relationship stories) so of course the artwork and the stories are to serve a woman's fantasy.
gacchi muchi is something in between because lately, around the late 2000s and early 2010 there is a small but steady stream of women that takes interest in men with muscles.

as for gengoroh tagame, he's one of the most iconic bara artist (he's a man)... and i daresay a legend