Everything you need to move to development. Your app icon design will be uploaded in the correct file formats based on your stated needs. Typically this means a layered RGB Adobe Photoshop or Fireworks PNG file that’s ready to be uploaded.
Since not everyone has the correct design programs to open these files (your developer will), you will also get web preview files in PNG or JPEG file formats.
Plus, you’ll get the full legal copyright, so the design will be all yours.