It's an Android emulator for your PC. Download Android applications and launch them from your Windows computer. It creates a virtual environment recognizable as the one in Android and selects a destination folder for installation files and archives. The utility manages all types of APKs.
APK Downloader is a free program that will allow you to download an APK file from the Android Market directly to your desktop rather than to your device. You can pick the app you want and you'll have the APK file on your computer, allowing you to sideload it onto any of your Android devices.