Alternative Rock is a genre of rock 'n roll that was developed during the 80's, but became popular in the 90's. Early Alt-Rock artists include the Pixies and the Violent Femmes, as well as early proto-Grunge artists like the Melvins and Green River. Alternative Rock did no make much commercial success until Nirvana's release of Nevermind, which not only broke out in the Grunge movement with Stone Temple Pilots, Pearl Jam, Soundgarden, and Hole, but also the Indie-Alternative scene for acts like Oasis, Dinosaur Jr, Red Hot Chilli Peppers, Green Day, Rage Against the Machine, and the White Stripes, Radiohead, the Yeah Yeah Yeahs, and Coldplay (from the Britpop, Indie, LA, Garage rock, and Art Rock movements respectively). Today, because of the death of Grunge, Indie-Alternative and Pop music have fought over the airwaves for the New Millenium, with the rise of Boy Bands and Pop Princesses, to the Indie-Pop acts of Franz Ferdinand and Hive. More recently, 'Powerpop' and Pop-Punk acts like All American Rejects, Fall Out Boy, and new Green Day have been at the forefront of Pop music, while groups like Kings of Leon, the Foo Fighters, and Modest Mouse have stood on the side of Art Rock, Modern Rock, and Indie Rock, all subgenres of Alternative.
Nirvana was grunge, Modest Mouse is indie, and Oasis is Britpop, but all are Alternative Rock. Much of Alt-Rock has been influenced by the Punk music of the late 70's, but not all Alternative rock falls under Punk Music, nor does much Punk fall under Alternative.