1. Rest files contains any extra files or plugins files.
2. Quickstart package which contains joomla package, template files itself and any thirdparty free products. Usage is same as installing joomla. Pretty much you will have same as our demo website as long as third party products used in templates are free.
3. Template files only, if you installed joomla from original joomla package then you need this file and install it from extensions manager to use the template.
If you used no:3 then you also need no:1 rest files package which might contain modules/plugins/custom styles/ .psd graphic files.
See you around...