A CDJ, or Compact Disc Jockey, is a digital music player designed for DJs to mix and manipulate audio tracks. It typically features a CD player, a digital audio interface, and controls for adjusting tempo, pitch, and effects. CDJs allow DJs to play music from CDs, USB drives, or digital files, making them versatile tools for live performances. Modern CDJs often include advanced features like waveform displays, looping, and hot cues, which help DJs create seamless transitions between songs. They are widely used in clubs and festivals, providing a professional platform for both beginner and experienced DJs to showcase their skills.