Undergraduate courses are courses you take in your first 4 years of college to get your undergraduate degree (BS, BA). These include both general college and those classes in your major. Postgraduate courses are those classes you take to obtain a Masters degree. You need an undergrad degree (thus post, or after, graduation) and admission to grad school to take these classes. Some schools have 5-year masters programs. They are a gift because if you stop school and go back it usually takes an extra 2 years full time to get. You obtain a higher degree (Masters). You can also continue higher education to a Doctorate degree, also post-graduate classes, which will take a couple of years longer in school. The degrees build. Of course, a Masters degree makes you more qualified in your field. And a Doctorate enables you to teach at a college level! Hope that helps you understand.