The .apk file is for Android like it is .exe for Windows. APK means Android Package, so the app can be installed or is designed only for the Android operating system.
Most of Android users install apps through Google Play, but this is just one marketplace for apps. Alternatively, you can have the same apps from the developer’s website as APK file.
1. Install APK on Android
Go to Settings > Security > and check Unknown Sources
Usually, this setting Unknown Sources can be found in Security, but for some models, this option can be found in a menu with a slightly different name.
2. Install APK on Windows
Use virtualization software like Bluestacks. Install BlueStacks App Player on Windows and then install the APK file.