If I were teaching you how to play golf, I would not determine whether you had met my standards by giving you a multiple-choice test.  I would put you out on the golf course to "construct your own responses" in the face of real-world challenges.  Similarly, in school we are ultimately less interested in how much information students can acquire than how well they can use it.   Thus, our most meaningful assessments ask students to perform authentic tasks.

However, these tasks are not just assessments.   Authentic assessment, in contrast to more traditional assessment, encourages the integration of teaching, learning and assessing.  In the "traditional assessment" model, teaching and learning are often separated from assessment, i.e., a test is administered after knowledge or skills have (hopefully) been acquired.  In the authentic assessment model, the same authentic task used to measure the students' ability to apply the knowledge or skills is used as a vehicle for student learning.   For example, when presented with a real-world problem to solve, students are learning in the process of developing a solution, teachers are facilitating the process, and the students' solutions to the problem becomes an assessment of how well the students can meaningfully apply the concepts.