This feature is available in Enterprise and Ultimate editions.
Templates are reusable stories/backlog items or defects that allow you to pre-fill commonly used fields and even define a starting set of tasks and/or tests. Templates give you flexibility when managing common, repetitive backlog items and their tasks across projects and their sub projects. They can save you time if you routinely create the same types of backlog items with similar information, or if you want to create several items at once.
Templates should be created in the projects in which they will be used. The list of templates you see will be all those in your currently selected project and below in the project tree. Use the copy function if you need to have a similar template in different projects.