Namespaces in Kubernetes allow objects to be grouped and can be used for logical groupings such as denoting multiple environments like dev, qa, or prod, or for grouping objects that make up an application. Namespaces can be created using the command line tool kubectl or using a YAML configuration file. Key points include: namespaces provide a mechanism for isolating groups of resources within a single cluster; namespaced resources cannot be created without a namespace; and effective use of namespaces can make cluster management more streamlined.