A Namespace is a way to scope both Permissions and Entity Attributes. Each Namespace instance is one level of scoping and is one record in the system. For example, KC or Kuali Financials could be a Namespace. Or you could further break those up into more finer grained Namespaces such that they would roughly correlate to functional modules within each application. Examples could be KC Rolodex, KC Grants, and Kuali Financials Chart of Accounts.
Out of the box, the system is bootstrapped with numerous Rice namespaces which correspond to the different modules. There is also a default namespace of KUALI.
Namespaces can be maintained at runtime through a maintenance document.