I can’t really explain it better than the popup help on that section so I will paste it here:

In order to improve performance and limit the number of HTTP requests per page load for all the forum CSS and script (JS) files, by default Simple Press combines or concatenates the CSS and script files into one CSS file and two script files (one for header and one for footer). With these options, you can disable this combining and force individual loading of each CSS and script file. This should not need to be done, but the option is provided for debugging or other rare cases.

Thanks Swordfish,but does this loader forums even faster if i turn these on?

Ken

There should be a small boost in performance – yes. Depending on a few other things though some hosts will not allow it but give it a try. You will see instantly when you reload the forum page if it is good for you to use.