With the add-in you can open a dialog, enter something like $y = \sum_{i=0}^n x_i$ and you will get an equation in your slide. This is done by embedding your Latex code in a template. Then, latex.exe is called in order to create a DVI which is afterwards converted in a PNG file by Ghostscript. The PNG is then inserted in your slide. Your Latex code is stored in the genertated PowerPoint object. Hence, you can edit your code later.