And Object, in this case (big O), is the name of a class. Not everything is an object, as someone said, there are also primitives. There are many other "thing

And Object, in this case (big O), is the name of a class. Not everything is an object, as someone said, there are also primitives. There are many other "things" in Java that are not objects (operators, statements, etc.). Kotlin does set some of this straight. Everything inherits (indirectly) from the Any class. And primitives do not exist in Kotlin (as in Ruby or Smalltalk).