What is a rubric?
A rubric is a scoring guide that helps teachers evaluate student performance, based on a range of criteria. A rubric lists the criteria, or characteristics, that student work should exhibit and describes specific quality levels for those criteria.
How is a rubric structured? Like a matrix.
A rubric is a matrix of criteria and their descriptors. The left side of a rubric matrix lists the criteria for the expected product or performance. Across the top of the rubric matrix is the rating scale that provides a set of values for rating the quality of performance for each criterion. Descriptors under the rating scale provide examples or concrete indicators for each level of performance.

Let's see an example...
