How to understand the definition of sequence limit?

At the beginning of advanced mathematics class, we talk about sequence , Including the definition of sequence 、 The limit definition of sequence and the characteristics of convergent sequence . The definition of sequence is easy to understand , But the definition of the limit of the sequence is about 1/10 I began to feel confused , Basically, I remain ignorant in the back ASCII 66 The state of . After searching several articles , I found that the following article is helpful for solving ignorance , Hereby forward ：

https://www.zhihu.com/question/347024216