Enter a term and subject abbreviation, like SP12 CS for Spring 2012 Computer Science.
If you do not enter a course number, you will be given a list of classes in that subject.
If you do enter a course number, you will be given the grade distribution(s) of that class.
If there are a list of classes to select from, there is now a Preview button that will allow you to drop down the grade distribution graph of that class :)
The first time you search a particular term, it will take a few seconds to load. Every sequential query for that term will be much faster, since the data is cached in your browser.