You can enter or update a grade from either the Grades tool or the assessment tool. However, changes made in the Grades tool are not updated in the associated tool. Changes made in the assessment tools are passed to the gradebook.
You can associate quizzes, submission folders, and discussions with grade items and grade them directly from the Quizzes, Assignments, and Discussions tools. You can create the grade item as you set up a quiz, dropbox folder, and discussion topic.