AC/DC is an Australian rock band and considered pioneers of hard rock and heavy metal music. The group was formed in Sydney, Australia in December, 1973. Their albums have sold in colossal numbers - the total is now estimated to be around 100 million copies worldwide.
AC/DC is generally divided into "Bon Scott era (1974-80)" and "Brian Johnson era (1980-present)". Some fans have a preference, others point to the merits of both singers and appreciate them equally.