The levenshtein() function is part of a set of functions that are used to look at the structure of a string depending on how the string sounds, using levenshtein() allows you to look at the total difference between two strings, defined as a distance value. The important feature of this is that you can compare one string to another and see if they are similar.
The levenshtein() function takes two parameters, these are the two strings that you want to compare with each other. If the two strings are the same then the distance is zero, the higher this value is the more distance there is between two strings. Here are some examples.