Assessment is the term we use to analyze and use data to make decisions about teaching and learning. In some cases, assessment can take on the form of discussion, for the sake of determining one's understanding. In other cases, assessment can take on the form of an essay, a quiz, or a competency test. In either case, an expert is determining how learners are able to demonstrate their understanding, and at times, application of the understanding.
When we assess student learning, we make judgments on how students are meeting the assessment criteria, often found in rubrics and competency tests. Assessment, however should be more than just making judgments; it is about determining where students are in their learning, and how to improve our instruction to support students to meet the course expectations.