Big-5 is basically the personally test that all researchers use. Personality tests in general have a bad rep since most know only about shitty ones.

big-5 has 5 traits that people can score from 0-100% in, oceanchat uses 5-dimensional euclidean distance based on your traits to make a similarity-score between you and the others, and match you up with the closest ones. well, if it gets any users lol.

if youre new to big 5: https://youtu.be/Pc8IDcRVPZ4