A B-boy is someone who practices break dancing, a physically demanding form of hip hop dance. Originating in the 1970's in the Bronx, break dancing is a highly improvisational form of dance in which the dancer utilizes moves that he has either invented or learned, such as the head-spin and the windmill (See references 1). Break dances often include a frozen pose at the end to show off the dancer's physical control (See references 1).
Certain types of hip hop dancing are characterized by a competitive aspect. Dancers, particularly break dancers, often perform in the middle of a circle of spectators. This can lead to "battles" between opposing dancers or even opposing teams (See references 2). There is no formal scoring method for dance battles---the winner is typically determined by the crowd's vocal approval or disapproval.
Locking is a form of hip hop dance that originated in Los Angeles. Invented by Don Campbell in the 1970's, locking is a dance characterized by short pauses that interrupt the dancer's moves (See references 2). It found a wide audience after appearing on the TV show "Soul Train" and earned its place alongside break dancing in the cultural canon of hip hop dance (See references 2).
Hip Hop, now considered a legitimate dance form, is now taught in dance conservatories and studios. Schools like the Hip-Hop Dance Conservatory in New York, which calls itself "the most intensive and comprehensive professional conservatory of its kind in the world," teaches the fundamentals of anatomy, auditions and professional choreography (See references 3). These schools prepare students for careers in hip hop dance performance and choreography for stage and screen.
Hip hop dancing continues to evolve and gain popularity along with the music and culture with which it is associated. New styles of dancing, such as krumping and clowning, continually break into the mainstream of hip hop culture and while dancers compete across the globe (reference 2).