Undergraduates are students participating in the general academic coursework of a college working toward a Bachelor's degree. This process usually takes four years. Some students take longer than because of various personal reasons such as taking break from school to work or changing majors. The 4-year standard is based on your school's definition of a full course load undertaken and passed every semester.
Undergraduate students take lower division classes during their freshman and sophomore years. The lower division usually includes what are commonly called the general prerequisite classes. General prerequisites classes cover a wide range of topics, including math, science, social sciences and the humanities. The goal of these classes is to make students more "well rounded" individuals, with a breadth of college level knowledge. It also allows students to test the waters in each of the school's fields to get a sense of what they ultimately want to pursue as a major.
Upper division coursework--the junior and senior years--includes a focus on more advanced classes in specific subjects. Upper division coursework is undertaken once a student has chosen a major and been assigned a faculty adviser from the major's department. Upper division courses often come with many more requirements for enrollment. For example, enrollment in an upper division English course often requires passing a test that gauges proficiency in writing. Upper division classes are also closed to students from other majors, unless they declare a second major or a minor in that discipline.
Graduate level coursework is study done after the completion of undergraduate studies. Enrollment in a graduate program requires a Bachelor's degree and recommendations from professors during undergraduate study. Graduate studies can conclude in a variety of degrees such as a Master's, a Ph.D. or an MBA. Students already in a professional field seeking to update their skillset can also enroll as nondegree seeking students. Coursework involves a mix of advanced classes, independent research and practical experience in the field. Graduate students also assist their advisers by grading papers and sometimes appearing as guest lecturers.