Can anyone explain to me the differences between how Emmy nominations used to work and how they work now?

I’ve been seeing stories all over about Family Guy being nominated for an Emmy. The stories start by saying that rule changes have allowed this to happen, because the new rules favor edgier content, and seeing this, Fox submitted Family Guy for nomination. I understand more shows are nominated per category as well. But that’s where most of the stories I read stop discussing what exactly the difference was.

Usually, they point out that no animated show since the Flintstones in 1961 has been nominated. Also, they point out the obvious, that the Simpsons, which in many people’s opinion (mine included) is perhaps the best most consistent show of any kind ever shown on television. But beyond decrying the unfairness of the Simpsons never being nominated in 20 years, and the shock of a program that makes a lot of puke and fart jokes actually getting a nod, the stories go no further.

So, what exactly were the old rules that kept shows like The Simpsons from getting nominated, and what exactly are the NEW rules that allow shows like Family Guy to get nominated? And why didn’t the Simpsons get the nod this year if Family Guy was able to be nominated, does it have something to do with the rules, or did they just not apply, thinking it wouldn’t matter yet again? What do you know, what have you read?