You can view an item of a data list to see its details and perform actions on it.
To view an item of a data list, find the item you want to view in the data list, and click on the item to open its details page.
By default, the detail page will show as a right sidebar pop-up window with default page layout. You will see all the fields and values of the item, as well as any attachments, comments etc.
You can change the form layout by adding a custom list form, and set it as the view item form.
You can also change size of the sidebar pop-up window from small, medium, large or full screen. Or, you can change the way to open detail page as a new full page.