I really did not know about rubrics until I started teaching at the college level.
Basically, a rubric is an assessment tool. It helps communicate standards of performance to students. This might be for an essay, term paper, speech or sometimes the entire course.
It informs the student ahead of time on what factors will be judged or graded by the instructor. The rubric consists of two components—criteria and levels of performance.
When I was teaching a class in public speaking, the speeches had a rubric so students knew what I was grading as they spoke. The criteria section might include body language, vocal variety, content, gestures, intro and summary, etc. Each of these sections would have a number value from 1 to 5 or 1 to 10.
At the end of each speech, it was just a matter of adding up the numbers to see how well each speaker did, and rank them against the other students.
It wasn’t until the mid 1900s that rubric took on the meaning it has for educators. Originally it was written instructions (penned in red ink) for religious services. Sometimes the term was used to describe the decorative text in medieval writings.
That wonderful, colorful cube of a puzzle on the other hand, is an entirely different subject.