All objects in the Kubernetes REST API are identified by a Name and a UID.
Names are user-provided. Only one object of a given kind can have a given name at a time. But if you delete an object, you can make a new object with the same name. Names are the used to refer to an object in a resource URL, such as /api/v1beta3/pods/some.name. Names may be up to maximum length of 253 characters and consist of lower case alphanumeric characters, -, and .. See the identifiers design doc for the precise syntax rules for names.
UID are generated by Kubernetes. Every object created over the whole lifetime of a Kubernetes cluster has a distinct UID.