One of the new feature available in SharePoint 2016 is Durable Links which provides resource id based links for documents. This feature protects the integrity of document links even if the document is renamed or moved to. When links to documents with resource id are used SharePoint 2016 looks up the document by resource id and opens in Office Online.
An example of how durable link in SharePoint 2016 works
1. User uploads a document named TestDoc.docx to a document library in SharePoint 2016 sites.
2. User shares the document to other users in his organization by using Share option in document preview page
3. An email is sent to users with the link to the document TestDoc.docx.
4. If you notice the link it will have a reference to the resource id like https://SharePoint Site /Documents/TestDoc.docx?d=wc0309c29bbf74b26be00d97cd54b9a79
5. Clicking the link will open the document in Office online web app
6. If the document creator changes the name of the document say to TestDocUpdated.docx the link that was shared earlier will work without breaking as office online loads the document based on the resource id