Ember.js server side or client side or both?

I'm a little confuse with Ember.js, I don't understand some basic concepts related to Ember. I see on the official page that Ember is a client side framework.

The reason for this difference is due to Ruby on Rails being a server-side framework, whereas Ember is a client-side framework.

Ember Doc.

But at the same time, I know that Ember run under Node.js which is a server side framework.

It is also true that with Ember I can build the views and components for the user's interfaces.

So, I'm very confused, It is Ember a server side framework, client framework or both sides framework?

Thanks.