Limit of sequence: When n approaches infinity, the sequence approaches that number infinitely. It can also be understood as: ignore the first few items of the series and consider the items behind the series. The more items behind the series, the closer to which number.

Function limit: when the independent variable is infinitely close to a certain number, the function value is infinitely close to which number. It can also be understood that when the independent variable is closer to the specified value, the function value corresponding to this value is infinitely close to the value next to this value.