Joomla 3.3 Template Manager: Styles Screenshot

In Template Manager: Styles screen in the Administrative Interface for Joomla 3, there is a button that reads "Duplicate". If you have a check mark next to one of the installed templates and you click on "Duplicate", you will see a new template appear in the list. This new template will have the same name as the original, but be followed by (2).

What is this Duplicate template?

This step created a duplicate STYLE, not a complete copy of your template files and folders. This style is still using the original template files and folders, but you can control certain settings that will be unique to this new style. This depends on the template you are using and how many things can be controlled for the template from the Edit Style screen.

Creating this duplicate style in Template Manager simply creates a new style in the _template_styles table of the database. This is good for changing things like fonts, background colors. It can also be assigned to certain pages on your site if you want some pages to have a specific color scheme or appearance. The module positions and overall layout will still be the same as the original template.

Creating this duplicate style in Template Manager will not protect you from overwriting customization to your template if you upgrade Joomla.

Creating this duplicated style in Template Manager did not create a new folder in your site's  template directory.

If you want to copy your entire template, rename it, and make it so that your customization will not be overwritten when upgrading Joomla, you must take a different series of steps. Click here to see this joom3 article on how to copy a template.