How does a frontend framework speak to a database?

I am learning some frontend and came across emberjs. It seems to be pretty interesting. I saw that emberjs has the ability to speak to elasticsearch directly and this has brought up quite a few questions for me.

1. How is it possible for a browser application to speak to an elasticsearch cluster? Is it implied that the elasticsearch cluster is exposed as a public interface?

2. I would think such an implementation would be browser application -> backend framework -> speak to a database. This seems like it is cutting off the need to have a backend framework? Am I incorrect?

3. Are there reasonable use cases for a frontend framework to be speaking directly to a data store?