There is a question in the collection part of the first chapter of senior high school mathematics that I am not sure about; What is the difference between inclusion and true inclusion in a set, and how to distinguish them? Inclusion refers to including the same set as itself and its contained sets, such as {1, 2,3,4}, {1, 2,3,4}, {2,3,4} and so on {1, 2,3,4}. The difference between true inclusion and inclusion is that true inclusion does not contain the same set as itself, so true inclusion cannot contain {1, 2, 3, 4} in the set, and others can.