Sift4 calculates the sift4 distance between two strings (how many characters are different) using the sift4 "simple" algorithm with a default max_distance of 5.
Sift4 - Super Fast and Accurate string distance algorithm. Unlike Sift3, Sift4 is not only more accurate but more closely reflects what you would get from getting the levenshtein distance between two strings.
Simple will take in two strings and return the string distance using the sift4 algorithm. It uses a default max offset of 5.