APK files, also known as Android Package Kit, are extensions used to distribute applications on Google's Android operating system. Although these files are mostly used on Android devices, they can be opened on several operating systems. APK files contain all the data of an application, from its resources and its manifest to the compiled application code of the application. If you have an Android device, chances are you've heard of an APK file at some point and wondered what it is. Understanding this is essential if you want to start downloading filtered apps or customizing your Android experience more than would be possible with the Play Store alone. The APK file is advantageous in many cases, such as for downloading geographically restricted or incompatible applications, or for blocking viruses online.
To bypass this download restriction and install them from unknown sources, you need to change some settings. To configure your Android device, go to the settings and navigate to the security option. Select the unknown sources option to allow the installation of those applications that do not come from the Play Store. Select and check the box next to the application options to warn you if you are about to install a harmful APK file. Search for an APK file on the Internet and download it to an easy to find location on your computer (such as your desktop).
Another way to force the installation location to sdcard is by using the adb install -s apk-to-install command. It's vital to understand this in order to download filtered applications and personalize your Android experience, which goes far beyond just using the Play Store. But it seems that a lot of people hate APK files because they're afraid of malicious and suspicious files outside the Google Play Store. It seems that the location of temporary files is likely to change from time to time and may vary depending on the operating system and what you are downloading. You won't get the APK file if you download an application from the Play Store. I ran into a problem that I couldn't find when searching for an application, but it was in My Apps so I could reinstall it on my new mobile phone;).
With this option, you'll only access healthy APK files to download.