What APK Installer does is find all the APK files on your device's memory, whether in the downloads folder or at any other filepath, and display them in a nice app list. From within this list all you have to do is press on the app's name in order to go ahead and install it.
Before installing any app, APK Installer offers you certain information on its APK. To begin with, you'll be able to see if the app is already installed or not. Plus, you'll see the APK file’s size and its version. Finally, you'll also be able to see the date the APK was last modified.
APK Installer is a very simple tool thanks to which you'll be able to easily install any app whose APK you already have with you. In fact, APK Installer doesn't really let you do anything you wouldn't normally be able to do, but it does make it easier for you to do it.