Post-graduate education (or graduate education in North America) involves learning and studying for degrees or other qualifications for which a first or Bachelor's degree generally is required, and is normally considered to be part of higher education. In North America, this level is generally referred to as graduate school. The organization and structure of postgraduate education varies in different countries, and also in different institutions within countries. This article sets out the basic types of course and of teaching and examination methods, with some explanation of their history.