The grid view (or thumbnails) gives a preview of the document behind the name. In a chaotic or disorganized drive, this can be very useful. If your drive is well-organized, this can be changed with a quick click of a button at the top of your list of files and folders. 

If you are still very new to using Google Drive, you may find you prefer the grid view, at least for a little while.

List View

Grid View