There are two types of assessment: (1) summative assessment;
and (2) formative assessment. Summative assessment is used
to grade students; summative assessment is generally carried out
towards the end of a course. Formative assessment is used to aid
learning; it is not used for grading and is normally carried out in
the early stages of a course.
A common form of formative assessment is diagnostic
assessment. Diagnostic assessment measures a student's current
knowledge and skills for the purpose of identifying a suitable
program of learning. Self-assessment is a form of diagnostic
assessment which involves students assessing themselves.
http://www.webster-dictionary.org/definition/assessment