I'm a bit surprised at your question... these are very different parts of one's university education. Could you tell us why they're confusing for you? http://www.thefreedictionary.com/undergraduate http://www.thefreedictionary.com/graduate http://www.thefreedictionary.com/Post-graduate

In the United States, the terms usually refer to university education. I'll illustrate the most common use of the terms by describing my own academic career. I graduated from high school when I was eighteen years old. I went to a public high school. My parents did not pay tuition. The school was supported by tax money and was free to everybody. I entered college, which in the US means the first four years of university education. It was a private university. My parents paid a lot of tuition. I studied for four years. During that time I was an undergraduate. I majored in mathematics. I graduated with a bachelor's degree. My diploma says that I hold a "Bachelor of Science in Mathematics." I then went to graduate school, at a different university. It was a state university, a public university. I had to pay tuition, but it was very low. I was a graduate student, or "grad student." I was doing postgraduate work. In the verb "to graduate," as in "I graduated," the "a" is pronounced as a "long A." I GRAD-you-ATE-ed. In the noun, "I'm a college graduate," or adjective, "a graduate student," it is pronounced as a schwa, something like "GRAD-you-it," but you hardly pronounce the vowel sound at all.

Undergraduate is someone , who has not graduated yet. graduate is someone , who has already graduated. postgraduate is someone , who is continuing his education after he got a degree.

An undergraduate is someone who is studying for his first degree at a university, called a Bachelor's Degree: "Although it's called a four-year program, it took me five years to earn my Bachelor's degree." A graduate student is someone with a Bachelor's degree who is enrolled in a Master's or PhD (doctoral) program: "After I finished my Master's Degree, I choose to leave university, rather than stay on to study for a PhD." A postgraduate is anyone with a Bachelor's degree who is taking further courses from a university. This includes graduate students in a Master or PhD program, but also other students with Bachelor's degrees taking individual courses without being enrolled in a program. "My company is paying for me to take some postgraduate courses so I can increase my areas of expertise." There are also postdoctoral university students, who have completed their PhDs. These students are usually heavily involved in research, but also take individual classes. "Dr. John Smith is a postdoctoral student at ABC University, conducting research into (a research subject) under Professor David Jones." Note: Bachelor's degrees are either Bachelor of Arts (abbreviated BA) for arts, humanities, and social sciences, or a Bachelor of Science (BS) for scientific and technical fields. It's the same for Master's degrees: "He graduated with a Bachelor of Science in Chemistry." "I have a MA in History." PhD stands for "Doctor of Philosophy," regardless of your field of study: "He just finished his doctorate in Music." "She has a PhD in chemistry."

i don't know