Popping and locking refer to dance moves that started as funk moves and are now used commonly in hip-hop dance. When popping, the dancer is forcing a part of his body outward in a movement that looks like a mini-explosion. When locking, the dancer is moving his body in a manner that is similar to contracting or tightening body parts into certain positions.
Locking was invented by Don Campbell and was originally called Campbellocking. Locking features distinctive stops in the movement. A dancer who is locking will stop a movement, locking his body into a position, hold it, and then continue at the same speed he was moving before. The movements are generally large and exaggerated. Additionally, the moves tend to be rhythmic and synced tightly with the music.
Locking is often thought to have inspired popping. Popping also involves a contraction, but the contraction is followed with relaxation, which causes a jerking appearance. Intensity levels may vary when popping. People also often use the word popping to encompass the styles ticking, strobing, animation, and waving and gliding, among others.
It is common to see the use of both popping and locking in one hip-hop routine. Because the movements often blend together within a single routine, it can be challenging to distinguish one move from the other.