Where do the four major components in android come from? What is the basis?

The four major components are derived from the Android official website development guide.

But everyone can't agree with others. From the perspective of actual development and programming, is there any basis? After careful analysis, in fact, the four major components need to be registered in the AndroidManifest.xml file, and they are all registered inside the tag, which means that the four major components are the portals for other applications to access the program, and they are also the first to be loaded when the app starts. of.