If it is one or two of the high numbers required for the postgraduate entrance examination, they only have different specific knowledge requirements and use the same books. More specifically, the knowledge required by high number one is more difficult than that required by high number two, and there are more things to understand in high number one than in high number two!
Advanced Mathematics 1 is a compulsory course for undergraduates of science and engineering, and Advanced Mathematics 2 is a compulsory course for some liberal arts except economics of science and engineering! The difficulty gradually decreases from one to four!
Personally, I think the main way to learn advanced mathematics is to read books, understand books and do exercises at the back of each section carefully. Because these questions are the most basic and an integration of concepts and theorems in the book. Only by firmly grasping the most basic things in the book can we improve and learn advanced mathematics on this basis!