This plugin checks the similarity between two strings of text. It implements stringSimiliarity.js for Bubble. stringSimiliarity.js is described as an "algorithm using the Sørensen–Dice coefficient to compare the similarity of two strings".
You pass two strings to the plugin and it gives a number between 0 and 1 indicating the similarity between the two - zero being no match and 1 being exactly the same.

One example use case is with a quiz question where the answer is free text. The plugin can be used to determine how close a given answer is to the required answer and you might decide for example that anything over 0.7 is a close enough match.