45 RPM records are a type of vinyl record that play at a speed of 45 revolutions per minute. They were introduced in the late 1940s and became popular for single songs, often featuring one track on each side. The standard size of a 45 RPM record is 7 inches in diameter. These records are known for their distinctive large center hole, which allows them to be played on specific turntables. 45 RPM records played a significant role in the music industry, especially during the rise of rock and roll, as they made it easier for artists to release and promote individual songs.