Significance of siging the app for enterprise distribution

I’m done developing an android app for tablets using Ionic. Now it’s time to deploy. So, I was wondering if I need to actually sign the app or if I can just pass on the debug APK to the client.

What is the difference between a debug build and a signed build, if I don’t need to upload it to the Play Store AND if I have already minified the debug build?

Depends on how you want to distribute the app.
Play Store => sign.
Public APK download or other store => also won’t hurt.
Customer on one non-public device => meh, don’r care.