What is excellent work? Sometimes, it is easier to just say "I know it when I see it." It may not be that the work has something wrong, it just might not have enough that clearly distinguishes it from others' work.
Some of your work may be graded holistically, where a descriptive term summarizes it. When it comes to calculating your final grade at the end of the semester, terms like "very good" cannot be used in a formula. Thus, every assignment will have a numerical grade associated with it. This brief page details how this number is determined.
The following are terms used to describe the grade. Each one could have a modifier, that is, followed by a plus or minus sign, to indicate how well the term describes the work. The "base" grade below are typical, though the instructor may alter the percentages (e.g., by 5%) depending on the assignment.
Additional modifiers can add or subtract points as needed. Typical modifiers include: late (e.g., -10%), need to leave comments for others (e.g., -20%), need to leave comments for everyone (e.g., some were left, but not all, -5%), and poor/repetitive comments for others (e.g., -3%). Modifiers cannot always be predicted in advance. For example, suppose you do not give your presentation on the day it is scheduled, and you come late to the class on the day that you do give the presentation. Typically, the late penalty would apply to either of these cases, but an additional penalty may be given in this case.
For presentations, I try to leave comments (positive and negative) for everyone. I may also include questions that I have, whether or not you answer them in the question/answer phase.
For example, suppose an assignment gets the grade "very good+" with a modifier of "late". The base is between 86 and 89, but the late modifier would typically reduce the grade by 10 points, resulting in a grade between 76 and 79.