A rubric is a tool that is used in self assessment and effective evaluation. "A rubric is an explicit set of criteria used for assessing a particular type of work or performance." (tltgroup.org)
What a rubric does is provide a multi-level framework for detailed assessment. In the same way as a graph there is a X axis and also a Y axis. Then at regular stages or intersects, a line is drawn and eventually a series of boxes beome apparent.
So a rubric uses multiple points of source data to create an overall picture of the subject. Evaluation moves from a yes/no strategy to a multi faceted approach that is far more robust.
The way we apply the rubric for evaluation is by comparing hard data against soft data. So on the X axis we apply a points scheme for quantitative data. Where a measure has been reached a value is given to the outcome. For example - if 30 sales are made within a month then that value may be 5, repeat sales equal 7 points and so on and so on. When a total is reached then a point is plotted on the rubric.
On the Y axis a self assessment exercise takes place. This is where reflective practice is carried out and the individual and their manager reflect on the qualitative data and create a value also. One factor may be the measurement of customer satisfaction for any given sale.
Interestingly - you effective evaluation requires the application and submission of evidence for both the qualitative and the quantitative.
So when we combine the X axis and the Y axis data points we have a point of reference in the rubric. Where rubrics differ from standard plot graphs is that the final outcome or result is dependant upon multiple factors and the final assessment or grade given falls into a described area rather than being a single data point.
For example - a rubric could contain quadrants. Poor, Average, Good, Excellent. Depending upon the X and Y scores the final data point will end up in one of those areas. Once the rubric has been completed - then you have a starting point from which to start making changes.
For more detail on creating a rubric I recommend you check out this video -