Yes, sort of (ambiguous answer I know) ;-)
It's a Content Management System or, more accurately in this case, a Course Management System (CMS) geared towards the education sector.
A CMS has a web browser based control panel that allows you to add, delete and otherwise edit the content of your site, from individual pages to complete email systems for multiple users, depending on the CMS and its features. Think of Dreamweaver or FrontPage embedded into a web page - that's how you edit site content.
I like Moodle - I've helped set it up for a couple of schools and it works like a charm.
Like any other CMS you can template the entire look of the site by editing just a couple of files. Unless you are familiar with PHP and MySQL you may scratch your head a bit when you first kick things off, but if you get stuck at all post your queries here or check out the documentation for Moodle on its own site and see where you go.