How to create White Square and Transparent Circle inside the square using Photoshop?

There may be several ways to achieve this, but this is my preferred method:

1. Open up a canvas of a suitable size.
2. Select the Rectangle Tool (U)
3. Holding the SHIFT key, draw a square to a size of your liking. Note, make sure you are making a shape shape layer
4. Now get the Elipse Tool (SHIFT+U)
5. Have your cursor on the bottom left corner of the square, and holding SHIFT, drag up to the top right corner of the square
6. CRTL click on the circle layer, then apply a layer mask to the square layer.

I think I understood what you are saying correctly. If not than, do everything up till step 5, then just set the "fill opacity" of the circle layer to 0.

Hope this helps. (: