Rubrics are rules or instructions, usually in a list, that explain how to do something or how something will be judged.
Rubrics are helpful because they tell you exactly what you need to do or what is expected of you.
Examples:
The teacher gave us a rubric for the project.
The rubric tells us how our work will be graded.
She followed the rubric to make sure she did everything right.
The rubric for the game was very clear and easy to understand.
The rubric for the contest was so strict, it was like a long list of rules.
I always make sure to read the rubric before starting any assignment.