Can you explain / give a link to an article about the process of signing an apk file?

Question

Android

Yes, I google badly, but I could not find a complete intelligible explanation of how the signing process takes place (not how to sign an application), namely what files are created, what is stored in them, how it protects against hacking, in fact, if you generalize, how with signature, the application is protected (I would like it in detail, that is, in general, everything that happens during the signature, and how then the verification of the signature and related files goes on)