We’re in the process of updating the documentation for Zotero 5.0. Some documentation may be outdated in the meantime. Thanks for your understanding.
What is the difference between Links and Snapshots?
When you attach a link to an item, Zotero stores only the page title, URL, and access date, and you need to return to the site to view the page content. When you save a snapshot, Zotero saves a copy of the page as it currently exists and archives it on your computer.