Not many are explaining the actual difference beyond what order you get them, though they did a good job of explaining order and whatnot.

Undergraduate degrees (most often 4 year programs that you see in TV and that most people "going to college" get) are a broad overview of a field. Someone who finishes is by no means an expert, but is ready to be trained on-the-job in their field. A biology major may have taken a class on animals which makes them ready to work in a zoo, where they will use their knowledge to help learn more job-specific information.

There are other degrees like associate's degrees, and those are usually a very in-depth job training (not the best way of describing). Or it's half of a bachelor's degree in a different field, most would not recommend this.

Graduate school typically narrows the focus of your studies, and typically makes you do a thesis (a large project or piece of work that takes one or more years to complete). After graduate school you become an expert in your field. Someone from the zoo would call you because you are an expert in animal digestive systems and our undergraduate, capable as they are, doesn't know what to do.

There are professional degrees as well, teachers get a 'professional' masters as do some other professions (social work, pastors, mental health professionals) the difference being that instead of a big project, they essentially do an internship.

There are also law and medical school, which are graduate programs where you learn to do law and medicine.