Relationship between the emberjs.com and the ember-cli websites

It is my understanding that ember-cli is part of emberjs. Given this, why is there a separate www.ember-cli.com website? What does it provide not covered by www.emberjs.com?

Also, the user guides at emberjs.com recommend different versions of the prerequisite JS packages than ember-cli.com. For example, for Node, emberjs.com recommends version 0.12 or higher while ember-cli.com recommends version 4.0.x or higher.

I’m new to Ember and just trying to figure things out a bit.

Thanks!!