A global template is a template that can be used by multiple projects and is not tied to any specific project.
To create a global template the user will have to go to Apps>Manage Apps in the top horizontal menu.
Click on Global Templates in the left menu bar and then click on Add a Global Template. Now you can fill in the details of the template you want to create .
The template will now be present in the list where you can edit ,delete or mark as favorite.
Using Global Template in an issue
You can open an issue and go to the response template section and chose the template that you wish to insert .