Formative assessment is a process by which teachers continually gauge the depth of students’ understanding of classroom subject matter and adjust instruction to address gaps in that understanding.
Whereas summative assessments are tests that evaluate the degree to which students have successfully learned all the material planned for teaching in a given time period (typically, one school year), formative assessment refers more abstractly to the ongoing process of assessing what students have and have not learned for the express purpose of adjusting instruction moment by moment to meet individual students' needs.
Formative assessment does not necessarily involve graded tests or quizzes. In its most helpful form, the formative assessment process makes use of classroom activities and discussions that require students to not simply answer questions but to also reveal the reasoning that led to those answers. Teachers can in turn parse their observations of these activities to ascertain individual students’ strengths and weaknesses so that they might help students address the specific mistakes they may be making or misconceptions they may hold.