The Course frameset contains two frames:
The left frame contains a navigation bar containing links to Course content areas, communications, and other tools. (Note that these links may be configured by the instructor or system administrator, so they may vary from Course to Course.)
The Course Content frame is the target frame for the navigation bar links. This frame defaults to the Announcements page.
Detailed help documentation explaining this frameset may be found at http://www.blackboard.com/docs/r6/6_1/student/bbls_r6_1_student/.