The Safari Zone triumphantly returns with a new twist!! :D
The Friend Safari is basically the Safari Zone, however you can only access the Friend Safari if you have a friend registered in your PSS.
It's very confusing, so bear with me as I explain. xD
The Pokemon that appear in your Friend Safari depends on your friend code. As you know, everyone has a friend code. The friend code determines what type of Friend Safari you have! It could be a Grass-type Safari, Electric-type Safari, Normal-type... any of the existing 17 types!
Unfortunately, you can't enter your OWN Friend Safari. However, if you are registered friends with somebody, you can access their Friend Safari. Evidently, the more friends you have, the more safaris you can access. Remember that Person A has to register Person B, and vice versa. I can't stress that enough. x)
The Friend Safari includes many rare Pokemon, even including some of the starters. They all appear at Lv. 30.
There is a rumour lurking the internet that the shiny rate increases in the Friend Safari, with comments such as 'Haven't found a shiny at all, and now I've found two in the Friend Safari' being said. 'Specially since there is rare Pokemon in the Friend Safari, it can be quite the experience. It's also confirmed that Pokemon can have their Hidden Ability, and have two perfect IVs. So, it can be quite the experience.
If you don't know anyone that has the game, the Database Community has a wide range of people that are happy to share their friend code with you.
'Fyou'd like to read more, click here.
Hope I helped. :)
Source: The things I've heard... (yes, I said all that info and I'm not even up to that yet. xD)