This is the name of the underlying java package that will be built. The package name is how Android figures out "is this new apk being installed a replacement for an existing app on the phone, or a new app." So, once you pick one, don't change it.
If he prefer, he can also see this from a "path to" on an hard drive. It's not what it is, but the behavior is the same.
Let's say that you've put a game in "c:\my adult games\renpy's ones\this game":
- Every time the game is updated, you put it on this directory, and boom, you can play the update.
This is "keep the same package name from start to stop of your project".
- If you decide to put another game in this directory, you'll create a big mess that will not works well, if it even achieve to works.
This is "you used a package name that is not unique enough, and is already used by another software".
- If once you decide to put the update in another directory, you'll have two version of the game on your computer ; the old one and the new one, each on its own directory.
This is "you changed the name of your package between two updates".
By example, if I was making a android port for, lets say my corruption mod, I would probably goes with
AON.mod.003.corruption
.
- "AON" is me, relatively unique.
- "mod", because well, it's a mod.
- "003" it's my third public mod (if I remember correctly).
- "corruption" is the name of the game.
That someone making a mod for corruption decide to name the package "[something].mod.corruption", there's 99% risk that it happen. Then, that he use "AON" as "[something]", it's unlikely, but it can still happen, reason why there's the
second uniqueness factor, the "003". There's, lets say 0.001% risk that someone name his package "AON.mod.[number].corruption", and add 0.001% risk that this number will be "003". So, if I count correctly, it make 99.9999999% chance that my package will be unique, what is near enough to 100% ; especially since after this, someone have to install both on the same device.
And it's the approach that should be followed when defining the package name:
[Author ID, whatever name or something else].[second uniqueness factor].[name of the game with possibly dots or underscore inside]