All master's degrees require the completion of a bachelor's degree and usually require an undergraduate GPA of 3.0.
Many schools also require taking entrance exams like the GRE or GMAT.
Admission to a master's degree is based on your previous studies in a relevant bachelor's degree, or a qualification or combination of qualifications considered to be equivalent.
If you gained your qualifications overseas, these will need to be assessed to make sure they are of an equivalent standard.
Taught master's degrees (also called course-based master's degrees) are much more structured, with students following a program of lectures, seminars and supervisions, as well as choosing their own research project to explore.