What it sounds like, and the records to hear it on.
Scratching is a DJ or turntablist technique used to produce distinctive sounds by moving a vinyl record back and forth on a turntable while optionally manipulating the crossfader on a DJ mixer. While scratching is most commonly associated with hip-hop music, since the mid-1970s, it has been used in some styles of pop and nu metal. Within hip hop culture, scratching is one of the measures of a DJ's skills, as in DMC World DJ Championship or IDA .