The Grades tool is where all student grades can be listed/entered for the entire course. This tool allows you and your students to track their progress in the class. Students will only be able to access their own individual grades.
The SpeedGrader is where assignments can be reviewed and graded.
There are multiple tools within SpeedGrader With each of these tools it automatically creates a comment box for you as shown below in a green box. It is not necessary to leave a comment with each tool though.
You can pinpoint to an area on the students' paper.
You can highlight an area on the students' paper.
You can free write on a students' paper in a text box.
You can use strike-through on a students' paper.
You can free draw on a students' paper.
You can annotate/select an area on the students' paper.