With this app, you are able to send whichever app you want from your phone's storage, to your friends, without a wifi connection. The default action is to use Android Beam, which utilizes Nfc and Bluetooth for the file transfer. However, if both of you have an internet connection, you can use third party apps, like Gmail and Google Drive, to share or store the apk file. You can also easily share the Play Store link of the app by selecting "share link".
The app is ideal for situations where you don't have access to internet, like on a hiking trip, or if you have a limited data plan. Or, if you just want a convenient way to share your new app with your friends.

Disclaimer: Before you share an APK, please make sure you have the redistribution right