Why do apps on the Google Play Store have com. at the start? When you get an app from the play store, the apps are always given in this format (For example):

play.google.com/store/apps/details?id=com.king.candycrushsaga

I'm not interested in the main URL, and just the app name, so I get:

com.king.candycrushsaga


I know that this is the actual app name, that is not the friendly name shown on the app drawer or in the play store, but the com. part always confused me. I know what the other parts of the name are for (com.PublisherName.AppName), but what is the point of the com. at the start?
The naming convention is derived from the Java standards, and is comparable to an URL, but in reverse. The key here is that it has to be unique, that's why it's so specific.

In you example, com is the main category which is comparable to a Top Level Domain, which can also be com. Next is the company name king, which can be compared to a domain name, and finally candycrushsaga, which could be a subdomain. Since the names have to be unique, this naming schema is quite usual, but can sometimes be divided even further by adding a subproject name to the end. For example King could separate games from other apps they've created by using the name com.king.games.candycrushsaga.

According to Java standards, the first component has to be a valid top level domain (com, net, edu, gov, country-specific), but I remember also seeing package names that didn't respect the standard.