Subscribing to a feed will allow content from another site into a section of your site. It will not replace your content but keep in mind you can't control the content in the feed. You can still add your own content to that specific section. The feed you subscribe to can co-exist with your own content.
You will not be able to curate any content that is fed onto your site. The feed will appear automatically once you subscribe to a specific source tag.
Cascade will allow content to flow from site to site without having to copy and paste to individual pages — it will be published from a central location. You'll be able to "subscribe" to other departments' tags, which allows their content to appear on your site. The most common subscriptions will likely be news, events, and stories.
No one will be able to subscribe to your content without your permission nor will anyone feed content into your site without you knowing. Any subscribing or tag sharing will need to be communicated outside of the Cascade system. If you have questions or concerns about how subscribing to content or feeds on your site will work, feel free to ask ITweb.