For creating a tracker, there are two steps. The creation is the first one and the configuration the second one. The specifities of each tracker (BTS or not, and other details) are filled in the configuration form.
The short name is used as the tracker ID. This name will be use in the mail interface or in the URL.
All the tracker's informations will be filled in the configuration's form (like description, associated packages, bugs...).
The usertag's fields will be available only if the user has checked the Use BTS option.