A graduate school may offer a range of degrees, including master's degrees, doctorates and professional degrees. Regardless which degree a student earns from a graduate school, it is called a "graduate degree."
In the United States, graduate degrees in medicine, law and business are typically referred to as "professional" degrees. Such professional degrees are frequently earned from professional schools that specialize in a field. Some fields, including divinity, architecture and fine art, dub their professional degree a "master's degree."
A master's degree usually takes two or three years to finish, while other graduate degrees may take longer. Master's students must take classes and pass exams, and they may be required to complete an internship. Some will have to write a dissertation or thesis entailing original research; others will have to pass a rigorous exam. Master's graduates develop skills such as critical thinking, analysis and research, which they must apply to their field of study. The most common master's degrees are Master of Science and Master of Arts, although some schools use Latin names.
These categories are general. For example, a Master of Science could be in agronomy, foreign service or biotechnology, to name a few. A Master of Arts could be in English, history, philosophy, theology, nursing or the social sciences.
Other graduate degrees have similar requirements as a master's---often more strenuous (such as a medical or doctorate degree). Some doctoral programs begin with master's degrees and allow master's graduates to continue working towards their doctorate. Doctoral candidates who do not complete their dissertation are sometimes awarded an additional master's degree, called Master of Philosophy.
Graduate schools may stand alone, or may be part of larger universities. Graduate schools generally accept applicants for advanced academic degrees only after applicants have completed an undergraduate or bachelor's degree.
What Americans and Canadians call a "graduate student" is typically referred to as a "post-graduate student" in Britain.