The Swedish Quartet, also known as ABBA, was a popular pop group from Sweden that formed in 1972. The group consisted of Benny Andersson, Björn Ulvaeus, Anni-Frid Lyngstad, and Agnetha Fältskog. They were one of the most successful musical acts of the 1970s and 1980s, selling over 380 million records worldwide. ABBA is best known for their hit songs such as 'Dancing Queen', 'Mamma Mia', and 'Take a Chance on Me'.