A graduate student is a person who goes to school after they finish their regular or elementary school program. They usually have to go through high school first, then attend university. A graduate student goes to school for even longer after university and needs to finish a big project or thesis to get a special degree called a "master's" or "doctorate" degree.
So, when you go to elementary school, you learn basic things like reading, writing, and math. After that, you go to high school, where you learn more advanced things and prepare for college. After graduating from college, some people choose to go to graduate school to study even more and become experts in a certain field. This takes many years to complete and is a big accomplishment!
As a graduate student, you might spend a lot of time doing research, writing papers, and working on projects. You'll have a big supervisor who helps you and teaches you everything they know to become really good at what you do. You'll also have a chance to learn from other experts and professors in your field.
Overall, graduate school is a lot of work, but it can lead to many exciting opportunities and successes in your future career.