Papers are the individual academic components of your entire "course" for a particular semester or year.
Each paper is identified by a seven-character code. The first four characters are letters which denote the subject area (e.g. ACCT for Accounting, PHSE for Physical Education) followed by three numbers (beginning with 1 for 100-level papers, 2 for 200-level papers, and so on); e.g. ACCT 101, PHSE 235.
Each paper has an associated number of points which contribute to the total that you need for your qualification. Most papers at 100-, 200- and 300-level are worth 18 points, but some have differing point values depending on the workload required.