Special use of item types for test
Any item type can be set up by an organization admin to work in ways that are specific to a test.
For example, the item must be set as a Test Case or Defect to operate within a test.
Test case — Items used as a test case have test steps and test case status fields, as well as work in test plans for users with a Creator license.
Defect — Items you use as defects work in testing for users with a Test Runner license or a Creator license.