Can someone explain US college system to me?

After successful completion of a high school diploma or GED you receive a grade point average (GPA). It comes in 2 forms: weighted and unweighted. Unweighted is always out of 4.0. Weighted classes will have extra points for difficulty. This includes Honours, AP, and IB. Next, you successfully complete the SAT or ACT exam. The SAT is out of 2400. The higher your GPA and test score the better the school you get in to, and the more likely you are to get a scholarship. After you begin taking classes at your university you fulfill the requirements for your major(s) and/or minor(s). Usually two years of general classes and two years of major classes. If you decide to go on to graduate school your college GPA is combined with your GRE (out of 340). Again, the higher each is the better of a school you get in to/the more likely you are to get funding. You can either apply for a Master's or go straight to a PhD (very unusual to get accepted with just a Bacherlor's). A Master's is 1-2 years. Usually 1 for humanities and 2 for sciences. If you move on to a PhD they look at what publications you had, your research experience, your GPA, and your GRE score. To complete a PhD is usually at least 3 years usually up to 6, and you must write a dissertation to achieve it.

It really is pretty simple. In the US they expect you to be well rounded and take classes outside of your major. This you do in your first 2 years plus you take beginning classes in your major. You concentrate on your major in the last two years but you can take some electrives. Undergrad means that you are in the first 4 years getting your BA. Graduate school is after you get your first degree (BA) when you study for higher degrees such as a Masters or a Phd.