It means that two elements are gradually approaching or infinitely approaching in a sense. When two sets are infinitely close, it usually means that the elements in the two sets are gradually close or infinitely close in a sense. In mathematics, when the elements in two sets tend to infinity with a variable, if their limit values are equal or the gap tends to zero, it can be said that the two sets are infinitely close, which is related to the concept of limit and the convergence of sequence.