An undergraduate degree results from completion of a four-year university course of study. Over the course of your undergraduate studies, you will choose a major subject and take courses that focus on increasing your knowledge and aptitudes within that major. You will also take a wide range of general education classes engineered to broaden your writing, reading, mathematical and critical thinking skills. Students who attend an undergraduate program usually leave with a bachelor of arts or bachelor of science degree -- B.A. or B.S.
Once you have studied at a four-year university and received your bachelor's degree, you will be able to look for jobs that may have once been closed to you. Leadership and management jobs, teaching jobs, military officer positions, and many other professional assignments require at least a bachelor's degree. Some careers will require a specific course of study; for instance, if you are planning on working as a teacher, it may be best to earn a bachelor's degree in education.
Graduate school generally lasts between two and three years, and consists of an expanded and more in-depth consideration of the things you learned in undergraduate studies. Graduate school usually has fewer general classes, and is more directly focused on what you want to learn for a specialized career. For instance, a post-undergrad education would likely be required for professions in the medical field, or for teaching at a university. Many business professionals have an MBA, or Master of Business Administration, and lawyers attend law-based graduate programs, often leading to doctoral degrees.
Careers that are unlocked with graduate degrees are often, though not always, higher-paying and more challenging than those available to holders of bachelor's degrees. Graduate school completion indicates that you are an expert in your field, and can help you negotiate for a higher salary or a more important position. It is also worth noting that many professionals earn their graduate degrees while already working in the field, attending classes at night and on weekends to improve their career options.