When you select a folder in the left pane, the Files tab of the right pane displays a preview of the documents in the folder. When the documents are SolidWorks parts, assemblies or drawings, or other graphical images, the preview helps you identify the document to select.
To display previews:
In the left pane, click on a folder.
In the right pane, use the horizontal scroll bar to scroll through the documents.
You can also click a document name in the file list to display its preview.