Rubrics articulate “… the expectations for an assignment by listing the criteria or what counts, and describing levels of quality from excellent to poor“ (1).
They let you define grading criteria with levels that you can select depending on how well each student meets each criterion. You can give feedback only (no numeric grade) or you can define points for each level, which automatically calculates a grade. In combination with Rubric uou can optionally leave a further individualised comment for each level, a summary feedback comment, and upload a feedback file. Rubrics can make marking fast, standardised and benchmarked, and can also help students to understand the marking criteria before they write and submit their work.
Rubrics contrast with Marking Guides (or Grading Forms in Turnitin) - the latter allow you to specify a criteria but instead of levels there is only a numeric grade to give.
Detailed step-by-step guidance on Rubrics is available from moodledocs.
See also:
References
(1) Reddy, Y.M., Andrade, H., 2010. A review of rubric use in higher education. Assessment & Evaluation in Higher Education 35, 435–448. doi:10.1080/02602930902862859