Moodle is a course management system (CMS) - a free, Open Source software package designed using sound pedagogical principles, to help educators create effective online learning communities. You can download and use it on any computer you have handy (including webhosts), yet it can scale from a single-teacher site to a University with 200,000 students.
The Moodle Website was created using Moodle, so exploring the site will give you a good idea of what you can do with it. Moodle can be downloaded for free from their website.
Now for the exciting stuff! Moodle is a software package that you can use to construct a class website or to manage distance learning features. It is designed in modules, giving you great freedom and flexibility to add content. You can access some demonstration courses in several languages on the Moodle website by clicking here.
You do need a server that would be accessible to your students. You cannot for example, house the course on your laptop - the students would not be able to access the course. Your school or district is bound to have a server, and if you are allowed (or encouraged) to have a class website, investigate the possibility of using Moodle for that purpose.
If you cannot use a server dedicated to your school or district, look into GlobalClassroom, a website that offers free hosting to over 2200 teachers and professors who wish to offer online components to their teaching.
Please watch this excellent video on which middle school teacher Molly Tipton explains how she uses Moodle in her social studies classroom.
