RateMyProfessors.com's ratings categories:
Easiness - Some students may factor in the easiness or difficulty of the professor or course material when selecting a class to take. Is this class an easy A? How much work do you need to do in order to get a good grade? Please note this category is NOT included in the "Overall Quality" rating.
Helpfulness - Helpfulness is defined as a professor's helpfulness and approachability. Is this professor approachable, nice and easy to communicate with? How accessible is the professor and is he/she available during office hours or after class for additional help?
Clarity - A professor's organization and time management skills can make a great difference on what you get out of the class. How well does the professor teach the course material? Were you able to understand the class topics based on the professor's teaching methods and style?
Overall Quality - The Overall Quality rating is determined by the average rating of the Helpfulness and Clarity given by all users. An overall rating of 3.5 to 5 is considered good (yellow smiley face). An overall rating of 2.5 to 5 is considered average (green smiley face). An overall rating of 1 to 2.5 is considered poor (blue sad face). The Easiness rating is NOT included when calculating the Overall Quality rating.
Rater Interest - There is always that one class everyone recommends taking before graduating. As a student, how interested were you in the class, BEFORE taking it? Or how interested were you in taking this course from this specific professor.