Run-D.M.C. was named after the two primary rappers -- Joseph 'Run' Simmons and Darryl 'D.M.C.' McDaniels (Jason 'Jam-Master Jay' Mizell was the third member of the group). They were the first successful 'new school' rap act, and started the crossover process, where rap began to be accepted as a legitimate music genre by mainstream audiences.
King of Rock was the group's second album, and was released in 1985. The album was produced by Russell Simmons and Larry Smith and was mixed by Rick Rubin. It took hip hop directly into the rock scene, by using guitars and drums as an integral part of the music. The result was something that sounded different from anything else out there, but which was accessible to rock audiences. King of Rock was a trendsetting album, but it was not a huge hit -- it reached #52 on the album charts. The single "King of Rock" did not chart on the Billboard 100.
The video, featuring Larry 'Bud' Melman (Calvert DeForest) from David Letterman did receive some airplay on MTV back in the day, which was a rarity for rap videos. For example, Yo! MTV Raps was not launched until 1988. Again, the video was not a huge hit, but it laid the ground work for what was to come.
Run-D.M.C. would go on to have huge success with their next album, 1986's Raising Hell, which included the top ten remake of Aerosmith's "Walk this Way." They remained at the forefront of the rap scene through the early to mid 1990s, at which point they gradually faded from view. The group officially disbanded following Jam-Master Jay's murder in 2002.