Assessment is the process of evaluating student work. It can take the form of tests and exams or be much broader. It can be formal or informal and can be a component of grading or can be disjoint from formal evaluations. This is distinct from evaluating the course itself or its instructor(s).
Instructors can evaluate and assess the work of students in many ways, formal and informal. Assessment may lead to marking/grading or be used in counseling and advising students. Assessment can result in numeric/comparative measures or in written or spoken advice to the student. Work can be assessed by the instructor or by the student's peers, such as members of a group. Assessment can be done orally or via written work.
Importantly, an assessment evaluates the work of the student, not the student him or herself.
Tests, are only one form used to assess the knowledge of students. Questions using this tag can ask about practices for creating or giving assessments of various types.
This tag should not be used for course evaluation or assessment of instructors. There is an alternate tag, tests that focuses on the narrower forms of assessment.