Ruby namespaces group definitions under nested names. `Tools::Hammer` and `Piano::Hammer` can refer to different classes without a name collision. Nesting also avoids concatenated names such as `ToolsHammer`, which can become visually cluttered. section 4.4.2
module Tools
class Hammer
end
end
Define a class inside a module, then refer to it through the `::` constant lookup token: `Tools::Hammer`. section 4.4.2
A name chain does not reveal whether its final name is a class, module, or plain constant; source or documentation provides that context. The containing name must be a class or module. section 4.4.2
Rake task namespaces
Rake groups tasks under namespaces: `admin:clean_tmp` identifies a task in the `admin` namespace. Nested namespaces can extend the task name, as in `admin:clean:tmp`. section 1.4.3
