A Master of Business Administration is designed to give students a firm grounding in the skills necessary for managerial roles in business. Most programs focus on several different aspects of the business world, including finance, marketing, accounting, negotiating, and strategy, among others. An MBA is a non-terminal degree, and there are some programs that ofter a Doctorate in Business Administration. The Master of Business Administration is effectively a professional degree, but the specialization or vocation that it prepares the student for is positions of responsibility in business.
Most Master of Arts and Master of Science degrees prepare the student to continue working in their field either by continuing their research and work by pursuing a doctorate, or outside of academe. These degrees are never terminal and don't usually enable the bearer to hold faculty positions at universities. Those with master's degrees do often lecture or teach in adjunct positions, however, whether or not they are pursuing their doctorate. Depending on the kind of study the student pursuing a master's degree is engaged in, there will be greater or lesser emphasis on vocational or professional study. For example, in some disciplines where there aren't a huge number of career options, master's degrees are effectively preparatory coursework for doctoral study.
Another one of the most common master's degrees awarded is the Master of Fine Arts. This is usually a terminal degree meaning that after it is awarded the bearer may teach at a university level. These programs offer intensive study and training of a specific fine art, like music, visual art, writing or film for example. These programs focus on craft and criticism, and the improvement of the student's creative work paired with some amount of academic study within their own field.
While the Master of Arts and Sciences, and the Master of Business Administration make up the majority of master's degrees awarded in the United States, there are other options, usually associated with very specific vocations. One example is the Master of Science of Education (MSed) that prepares students to be administrators in educational institutions. A Master of Public Affairs is a course of study on policy making and governance. There are a multitude of other master's degrees, each with it's own specific focus.