Meaning of R.layout.activity_main in android development (JAVA language)

Question

What is the meaning of R.layout.activity_main ?

I understand that \".\" operator is used to define variables of a particular object but in this case its been used t

Answer 1

In Android R is an Java-class that is auto-generated from your resources by the build process.

The R.layout member is a auto-generated class that contains all IDs for layouts.

R.layout.activity_main is a static final int member that represents the ID of the layout-file in layout/activity_main.xml.