Another component or application can reference a component by adding <myNamespace:myComponent> in its markup. For example, the helloWorld component is in the docsample namespace. Another component can reference it by adding <docsample:helloWorld /> in its markup.
Lightning components that Salesforce provides are grouped into several namespaces, such as aura, ui, and force. Components from third-party managed packages have namespaces from the providing organizations.
In your organization, you can choose to set a namespace prefix. If you do, that namespace is used for all of your Lightning components. A namespace prefix is required if you plan to offer managed packages on the AppExchange.
If you haven’t set a namespace prefix for your organization, use the default namespace c when referencing components that you’ve created.
The code samples throughout this guide use the default c namespace. Replace c with your namespace if you’ve set a namespace prefix.