Functions and properties can be declared as private. These are only accessible by other stuff inside of that class; they are inaccessible anything outside of that class.

In this case, something() is private, so we cannot call it from main(). We can call something() from somethingElse(), as both of those are functions on Foo. And, since somethingElse() is public (the default), we can call somethingElse() from main() and therefore indirectly call something() from main().

You can learn more about this in:

• the documentation
• Elements of Kotlin