A major (also known as a major concentration or concentration) is a term most commonly applied to a program of study leading to a bachelor's degree. Many schools do not allow you to officially declare your major until the end of your second year so that you experience a broad range of courses that will help you choose the most appropriate major. And some majors have limited enrolment, so in fact you may even be required to apply to get in to the major you want, including attending an interview or writing an essay. Community and career college programs generally do not have majors as such. Their 1- to 3-year diploma and certificate programs carry a designation, for instance Graphic and Digital Media Design Diploma, which is much more specific than, say, Bachelor of Fine Arts or even Bachelor of Design.
Often, students in a community college or career college program--sometimes all the students in the department--will take a common set of core foundational courses in the first year (or term, in the case of shorter programs) which then enables them to pursue a specialized area of study. But generally the field of study at the community or career college level is job-focused to the point where students do not take "elective" courses as they do for bachelor's degrees. Hence the designation of the diploma effectively stands in for the "major."