title: What is Android keystore file, and what is it used for?
body: <p>This is a general question, but particularly I am interested in it's use for Android. What is a keystore file, and what is it used for?</p>
  
  <p>Can multiple Android applications use the same keystore to sign their application (what exactly does it mean to "sign" an .apk?), and what are the implications (if any) of this?</p>