It was last published in 2011 by Charlotte Danielson as an Evaluation Instrument for teachers. It "identifies those aspects of a teacher's responsibilities that have been documented through empirical studies and theoretical research as promoting improved student learning." So in a nutshell it helps teachers with the HOW question when it comes to teaching. How to begin planning a lesson, how to manage a classroom, how to actually teach the students, and how to fulfill professional responsibilities. It is divided into four domains, each with varying numbers of components and elements built within. It is an intricate but helpful tool for pre-service and current teachers.