Why do internal links look like that?
If you're working with Linkit and internal links then you've most likely seen links in either of these formats: /node/999999 or /group/999/content/999999. These are considered internal paths. Both formats function the same way, the first one is available to School level pages, the second one to Groups, e.g., Centers & Institutes.
Internal paths are made of a Node ID which is a unique identifier for the content they represent (an article, page, event, etc.). In the case of pages within a group, they are made of the Group ID and the Group Content ID (in reality, group contents also have a global Node ID but that's getting too in the weeds).
In contrast, public paths are readable and informative. They are often made of the title of the content and the section it's in, e.g.: /about or /centers-and-institutes/example-center/about.
This results in two types of paths that lead to the same content:
Note: These are only example URLs and either don't exist or don't work.
The importance of internal paths lies in that they are unique and are bound to the content, not to the public path. Meaning that even if the public path were to change, the internal path will still point to the content page selected.
For example, if we link from our Homepage to our About page using the internal path, our About page can change from /about to /about-us, and the link will continue to work without a problem.
Does the public see internal links?
No, internal paths are converted automatically by Drupal into their public counterpart.
Continuing the example above, if your internal URL is https://publichealth.jhu.edu/node/999999, external users will see instead: https://publichealth.jhu.edu/about-us.