Street photographers strive to capture the life and culture of city streets, searching for what Henri Cartier-Bresson, probably the most famous street photographer of all, termed the ‘Decisive Moment’.
When it comes to street photography, many photographers traditionally choose to work in black and white, focusing the viewer’s attention on the subject by eliminating the distraction of colour. Wide angle lenses are used by photographers who like to get in close to the action, a method that encourages interaction between the photographer and subject. Another technique is use a lens with a long focal length to take photos from a distance and throw the background out of focus.
source: http://www.smashingmagazine.com/2008/12/14/the-beauty-of-street-photography/