In the same way that the CD players used by DJs have more options than a regular Hi-Fi CD player, VirtualDJ has more options than a simple media player like iTunes. They need special controls like crossfaders, loops, effects, etc, in order to “mix” the songs.It is used by DJs to replace their turntables and CD players, and use digital music instead of vinyl and CDs. Because being a DJ is more than just pressing play, DJs cannot just use iTunes or Media Player to perform a mix.
VirtualDJ is the application that DJs use when they want to use a computer to play their music.
