How is the URL for each page determined?

If you have set a permalink in the admin, it will be the URL, and for articles that do not have one, it will be the page ID.
For the following share URLs
https://www.notion.so/nabettu/Anotion-Q-A-c852ff3442c44ce18bc9a6bee3b5e85a
The last - after the above URL is the page ID as shown below.
c852ff3442c44ce18bc9a6bee3b5e85a
 
Therefore, on Wraptas
https://sample.wraptas.site/c852ff3442c44ce18bc9a6bee3b5e85a
the article can be accessed with the URL