Street photography is an approach to photography rather than a location, although the streets are the usual place that it happens.
"When I saw the photograph of Munkacsi of the black kids running in a wave I could not believe such a thing could be done with the camera." I said damn it, I took my camera and went out into the street. " Henri Cartier-Bresson
Alternately it is referred to as no rules photography. The plethera of equipment (tripods, lenses, filters, lights etc etc) associated with "serious" photography is left at home, or better still in the camera store. Its just too heavy and bulky to cart around, takes way too long to set up and by the time it set up the moment is gone.
Street photography is shooting from the hip.
Likewise the rules of photograph, the f stops, the shutter urges, the rule of thirds etc etc are left in their dust jackets on Amazon shelves. By the time all the technical considerations are taken into account, the birdy is in another country.
Thank Canon, Nikon, Fuji et al for point & shoots.
It is just the camera and the photographer with their enthusiasm, intuition and open mind.
Street photography can be and often is: Out of focus; A tilted horizon; A soft focus.
Street photographers are optimistic, for them the glass is always half full. They go out on a photo shoot with no plan in mind secure in the knowledge that this wide world of ours will provide. A subject, a situation, a scene will present itself all they have to have is the presence of mind to capture it when it does.
Street photography can be and often is: Odd things in the foreground; No central focus; Odd crops.
Street photographers see the usual, the everyday with fresh eyes. The reflection in a rain puddle, the colors in a crowd, the balance of a negative space. Their minds are open to all the stimuli that they see and they curse the days when they leave their camera at home.
Street photography can be and often is: very busy; A tilted perspective; Upside down.
Street photographers are not only on the streets, they are at weddings, school concerts, next to you on the train. They look a lot like tourists, its their favorite cover but they are one without the big flash. It was left at home, the available light will do.
Street photography can be and often is: under exposed; Blurred; Suffering from vertigo.
Street photography is, what all photography is, a snap shot.
What shines through is the photographer, his / her interpretation of the scene, what they see in the situation, their reaction to the stimuli, the art they see in the every day.
Technicians take technically correct and often pretty pictures.
Visual artists, whatever their medium, create images that stimulate the mind, the heart and validate the human condition in all its guises. Because, after all, pretty is in the eye of the beholder and consequently very subjective, whereas art speaks to all who are prepared to listen.