CK-12 provides two options to assess knowledge of concepts: Practice and Quizzes. Both may be used while learning different concepts.
Practice focuses on skill building and solving problems related to a concept. Helpful resources and recommendations are provided for those that are struggling with any given concept.
Practice is not timed, multiple attempts are allowed, hints, scratchpad are available and feedback appears immediately.
Quizzes focus on determining preparation and retention of knowledge. Quizzes include a certain number of questions from any number of concepts.
Quizzes on CK-12 do not include videos, hints, scratchpad, recommended resources and peer help. Quizzes can be timed or untimed and feedback appears at the completion of the whole activity.