This end user SharePoint Tutorial shows you how to create a site template from a SharePoint site. Site templates can be used to create a SharePoint site which is based on custom settings using the user interface.
After creating and editing a SharePoint site you can save it as a template and reuse it when creating new sites. The changes made will be reflected in the new site. Go to site settings and select save site as template. There you can set a new name and select if the content should be inlcuded too. After saving the template you can go to site settings and create a new site using the custom template tab.