When using SharePoint Views, you also have the option to enable previews of the selected items.
If an Office Web App preview server is available, previews will use the OWA server side technology where possible for selected file.
The Office Web App Server is available in Office 365, SharePoint 2013 or SharePoint 2010,
In the event a file is not supported by the OWA preview technology or an OWA server has not been configured, a preview is rendered using a local preview technology. There are a number of governance and control settings available for local previews to ensure maximum performance.