XF 1.1 Query about facebook integration

Hi chaps, i am a new user. I have setup the facebook integration, but had a few queries.

In the facebook approval box, what exactly does it mean by 'this app making posts on your timeline?'

Why would we need this and can it be turned off?

Secondly on the screen below, why would we need to post on there behalf? Can this be disabled?

Basically I am trying to make the facebook integration less scary looking to users.

Any advice is appreciated.