There are two main forms of assessment for learning, these being formative or summative assessments. Both are highly valuable in the classrooms as means of checking the learner progress.
Formative assessment is the variety of assessments taking place during the lesson, such as the traffic light system, where learners show their level of understanding using red, yellow or green cards (red being not at all confident, green being totally confident), or by giving each other two stars and a wish (two good things they have done, and something they need to improve on).
Summative assessments are the assessments that take place after the learning has occurred, such as exams or tests. These are ideal for a teacher to gauge how much learning has taken place, and allows them to see which areas of the learning were successful and which were not. National tests and qualifications all come under summative assessments.