Expanded Tables mode provides one more method of editing tables in Dreamweaver. Expanded mode is basically Standard mode with a magnifying glass effect, so that you can better see the edges between cells and therefore select exactly the cell or group of cells you desire, and then make the edits you want. This is especially handy when you have tables within tables within tables for layout purposes, and you want to be sure that you have exactly the right selection.
However, this mode doesn't have a feature set with any editing tools that you won't also find in Layout mode or Standard mode.