Beginner Question on Installing/Uninstalling Apps

[Excelsior]

Once you buy an application, for example, from the Google Play store, can you
install and reinstall the application?

My understanding is that the file is an "APK" file.

Do you get to keep this  "APK" file, so you can reinstall it later(especially
if you delete it )?

If not, how do you get the program back again, once you delete it?

[Drew]

It's tied to your Google account.

http://support.google.com/googleplay/bin/answer.py?hl=en&answer=113410

You could also use a backup app saver like "App Backup & Reinstall" or "My Backup Pro"