The grade type is the value that will be entered into the Moodle gradebook. Assignments allows for three grading choices:
Choosing None will inhibit the Gradebook from adding a column for that assignment activity.
Selecting Point will allow you to set a maximum point value and choose from three grading methods to determine the point value (see Assignment Grading Methods):
Simple direct grading
Scales are subjective, non-numeric scales that will be sent to the Gradebook. Scale grades will not be used in mathematical grade calculations. There are several predefined scales to choose from (thirteen in Moodle 3.2, ten in Moodle 3.0, eight in Moodle 2.8). You can also make your own scales inside the Grades tool. See Use a Scale for Grading Activities for more information on using scales and creating your own scales.