It is very important that we need to understand what is mean by spectrum, before going to the discussion on 5G spectrum. It is nothing but a group of signal or carrier which is having a predefined frequency. In a common man language , this group of signals or Carriers are the medium which carries the information from one place to other place. This information may be voice or data in mobile communication.
You can follow this link to see some 5G use cases an overview and Roadmap to 5G spectrum: