What does eight-character marriage mean?

Eight-character marriage refers to a method to measure whether the marriage relationship between two people is consistent through eight characters. This paper makes a comparative analysis of their birthdays (heavenly stems and earthly branches combination at the date of birth) from the aspects of yin and yang attributes, Tibetan elephants and zodiac signs. So as to determine whether they are suitable for marriage and predict their complementarity, stability and happiness after marriage.