Item types
Item types are the templates for sets used within each project.
While sets are unique to each project, item types can be used in projects across the entire organization. Item types can't be customized for individual projects.
Each item type can be configured to best fit your organization and methodology. The fewer item types that your organization creates, the easier it is to manage items.
Additionally, every item type is automatically assigned an API ID for reporting purposes, which can't be specified or changed.