When we write evaluations, we consciously adopt certain standards of measurement, or criteria.
Criteria can be concrete standards, like size or speed, or can be abstract, like practicality. When we write evaluations in an academic context, we typically avoid using criteria that are wholly personal, and rely instead on those that are less "subjective" and more likely to be shared by the majority of the audience we are addressing. Choosing appropriate criteria often involves careful consideration of audience demands, values, and concerns.
As an evaluator, you will sometimes discover that you will need to explain and/or defend not only your judgments, but also the criteria informing those judgments. For example, if you are arguing that a Mexican restaurant is excellent because (among other reasons) the texture of the food is appealing, you might need to explain to your audience why texture is a significant criterion in evaluating Mexican food.