Package names
The first thing that you will come across is something called a Package Name. It's quite easy to understand actually. A package name is simply like a reverse URL. Think of a package name as your app's domain name-just like a website, only in reverse. For instance, you can think of www.google.com as a website's domain name; in exactly the same way, the naming convention of an Android app is the reverse of a website. So, you can name your app something like com.google.www. There is no strict rule that says that your package name must start from com, but it is the most commonly accepted convention. You can also name your package name randomly using your own set of conventions, such as abc.xyz.lmn, mygame.mycompany.myname, and so on. Also, it is extremely important to note that package names must be unique and should not match the package name of any other existing app on the Google Play Store.
It is very important to choose a unique package name since the URL gets indexed by Google and is crucial for your game or app to be noticed on the Google Play Store. So, ensure that you use a unique package name for your game. Also, another interesting fact is that you can predict your app's URL even before it goes live if you have finalized it on your package name. For this reason, you cannot use the same package name of another app since it's already live on Google Play Store. Your app will be live according to the following URL convention:
https://play.google.com/store/apps/details?id=*package_name_here*
So, if your package name is abc.xyz.lmn, then your app's URL will be as follows:
https://play.google.com/store/apps/details?id=abc.xyz.lmn