what does 'objects being subclassable' mean?

Question

Dive into Python -

Different programming languages define “object” in different ways. In some, it means that all objects must have attributes and methods; in others, it means that all objects are subclassable. In Python, the definition is looser; some objects have neither attributes nor methods (more on this in Chapter 3), and not all objects are subclassable (more on this in Chapter 5).

I am coming from C++/Java background.

Answer 1

To be subclassable means that you can inherit from them. e.g.

class Foo(object):
    pass

object here is subclassable because Foo can inherit from it.