Private Pages/Posts etc For Certain Users Only

First: my apologies if this is a WordPress issue. Not sure, being a newbie to both WP and Atahualpa.

I'm building a gratis community website for the Beechwood Billycart Classic. This event has an organising committee. I'd like to let them Register as a User with certain privileges, eg adding posts, pages etc, BUT in a "Organisers Only" area of the website.

I've been reading up on "Roles and Capabilities" at wordpress.org, maybe making them "Authors" would do the trick, but I don't really know.

However, how can I make a whole section of the site only available to these Organisers? This would be an area which is not publicly accessible, but let organisers access it to discuss issues solely to do with organising the event. Maybe create a separate subdomain???

As I don't know where to start, I was hoping to get a few suggestions on how to go about this, or links to other resources that I could study.

MTIA