Noob question, forgive my ignorance

Hi all. I’m trying to do some research on various tools available that allow someone to develop games across multiple platforms.
After some searches for 2d engines I found myself here.

My interest is to hire out a developer to publish a game for android ios WP and w8 and so far I think I understood that cocos2dx does this.

I’m just a little confused because it seems the cocos name is available under other projects
http://www.cocos2d-iphone.org/
http://www.cocos2d.org/

So I’m wondering if there is any relation. The iphone site looks like it has similar branding but if 2dx supports all platforms why have an iphone only version?

Thanks for puttin up with a noobie