File Extension: .apk
An APK file is the file format used to install the applications on android operating system. A program in android is first compiled, and then all of its parts are packaged into one single file to make it an APK file. APK files can be saved in compressed zip format, with any decompression or unzip tool it can be opened. You can either change the extension to .zip or open the file directly using unzip tools. They are a type of archive file. When you are downloading and installing an android application then actually you are installing an APK file. You can install an APK file directly from a desktop, or from within a file manager app without downloading. By default, ability to install from desktop, or file manager app is disabled for security reasons. TO enable it, you have to change the setting of ‘Unknown sources’ from settings.