Editor:
In Simple terms:
It edits (and CSS, PHP, etc. at least most do) files, and you have very little power with it.
A CMS:
A CMS is a Content Managing System that is installed on your Web Server(Your Web Host) and runs your site thought MySql and PHP.
Now relax. You don't need to know MySql, PHP, or even and CSS(But knowing them do help, actully and CSS help a lot).
To try different CMS go here:
http://php.opensourcecms.com/
Once you see it you should under stand what it does.
I suggest Modx CMS:
Site:
http://modxcms.com/
Try:
http://php.opensourcecms.com/scripts/details.php?scriptid=48&name=MODx&page=1&sortby=dateasc
I would explain further but it would take hours.
-FireDart
P.S: To run a site larger then 10 pages, I would use a cms. Big sites like: CNN, Google, MSNBC, ESPAN,etc.. Use CMS's.