The 360 icon appears on a thumbnail when the thumbnail is actually a turntable, a series of images that allow you to view the 3D model from various angles.

When you click such a thumbnail, a turntable image series loads in the Preview Window and plays automatically. A scrub bar also appears at the bottom of the image where you can manually scrub the bar to turn the 3D model and view it from various angles.

If the Image Viewer icon appears at the upper right of the image, you can click this icon to open the Image Viewer and view the turntable at a higher resolution.