In view mode, someone who is not logged in can see the charts and mouse over to see tooltips of values, zoom in and out on charts, and scroll through columns in the table. When in view mode, they cannot create new charts or new table queries to explore the data. View-only visitors to the report link won't be able to click on a run to get to the run page. Also, the view-only visitors would not be able to see the share modal but instead would see a tooltip on hover which says:
Sharing not available for view only access.