Sizes included and where they are used
ios-1024.png is the App Store icon. ios-180.png is the iPhone home screen icon at 3x, ios-167.png is the iPad Pro icon and ios-120.png is used on 2x iPhones and for Spotlight. android-512.png is the size Google Play asks for on the store listing, and android-192.png matches the largest launcher density.
Recent versions of Xcode can build every iOS size from a single 1024 pixel icon, so for a new project the 1024 file may be all you need. Older projects and some build tools still expect the individual sizes.
Why the iOS icons are square and opaque
iOS applies its own rounded mask to app icons, and the App Store does not accept icons with transparency. So the ios files ignore the corner radius setting and are flattened onto your chosen background, or white if you picked none. Draw your artwork as a full square and let the system round it.
The Android files use the corner radius and background exactly as set. Google Play also rounds listing icons itself, so if you plan to upload android-512.png there, a radius of 0 avoids rounding twice.
Getting a clean result
Start from a square image of 1024 pixels or more; SVG artwork is rendered at 1024 first. Keep the important shape near the center and leave breathing room with the padding slider, which starts at 12%. Avoid small text, which disappears at 120 pixels, and thin lines that blur when scaled down. A bold silhouette on a contrasting background reads well on both light and dark home screens. Check the size grid on the page, where every icon is previewed with your settings, before downloading the zip.