Street dancing classes explained...

Hip-hop dance refers to dance styles primarily danced to hip-hop music or that have evolved as part of hip-hop culture. This includes a wide range of styles notably breaking, locking, and popping which were developed in the 1970s by Black and Latino Americans.

What separates hip-hop dance from other forms of dance is that it is often freestyle (improvisational) in nature and hip-hop dancers frequently engage in battles—formal or informal freestyle dance competitions.

Explanation supplied courtesy of http://en.wikipedia.org/