The Assessment area is where the instructor builds quizzes and tests, grades tests and other assignments, and keeps a grade book. There are 9 major areas in a Blackboard class. Most of these areas may be turned off if the instructor doesn't want to use them. Course Information could contain items such as the syllabus, or perhaps a reading list. Course Documents could have readings, links to websites, etc.
Assignments contains assignments.
When a new assignment is added, a new announcement is added to the Announcements page. Communication gives both the instructor and students the ability to send email, read the student roster, see the class-based homepages of other students and student groups, join a discussion or chat. External Links is a specific location within the class where the instructor may post links to external websites. Student Tools is an area where students may turn in assignments, edit their course homepages, change their information, check their grades, look at the student calendar, and read a student manual. Visible only to the instructor is the control panel which is where the instructor adds content and controls the course.