ABBA are a Swedish pop group formed in Stockholm in 1972 by Agnetha Fltskog, Bjrn Ulvaeus, Benny Andersson, and Anni-Frid Lyngstad. The group's name is an acronym of the first letters of their first names. They became one of the most commercially successful acts in the history of popular music, topping the charts worldwide from 1974 to 1983. In 1974, ABBA was Sweden's first winner of the Eurovision Song Contest, with the song "Waterloo", which in 2005 was at chosen as the best song in the competition's history as part of the 50th anniversary celebration of the contest.During the band's main active years, it consisted of two married couples: Fltskog and Ulvaeus, and Lyngstad and Andersson. With the increase of their popularity, their personal lives suffered, which eventually resulted in the collapse of both marriages. The relationship changes were reflected in the group's music, with latter compositions featuring darker and more introspective lyrics. After ABBA disbanded, Andersson and Ulvaeus achieved success writing music for the stage, while Lyngstad and Fltskog pursued solo careers.