The official statement would be that street photography is a genre of photography that captures candid, unposed, and often spontaneous moments of everyday life in public spaces, such as streets, parks, and urban environments. It typically focuses on the people, architecture, and culture of urban areas, and seeks to capture the essence of a moment rather than staging or manipulating it.
But ask 10 different photographers, and each will have their own idea of what street photography is. And it's highly likely that all of them will be correct.
In fact, the definition is slippery enough that I made a whole video about it, and about why some of what we call street photography might not be street photography at all.
In my work, I emphasize candid street photography: people photographed in public places, in unposed, candid situations.
As part of documenting the scene, I'm always looking to add some small twist to it, a moment that elevates it from a simple happening.
Like the expression on the face of the man holding the cross, and the two hands in the foreground. Without these two elements, the photo would lose much of its impact.

THE MOST COMMON STREET PHOTOGRAPHY STYLES
Street photography is an art form that captures the essence of everyday life, and style is how you convey your personal interpretation of that life through your images. There are several styles, or photographic focus areas, in street photography. Here are some of the most common:
Candid street photography. The essence of the moment: capturing people in natural, unposed situations, often emphasizing their expressions, gestures, and body language.

Urban landscape. This style highlights the architecture and environment of the cityscape, often emphasizing patterns, lines, and shapes.

Documentary street photography. This style seeks to document a specific event, situation, or social issue, often with a focus on the people and their experiences.

Street portraiture. Capturing portraits of strangers on the street, with an emphasis on the subject's character or personality.

Layers. One of the common approaches in street photography is to use layers. With higher aperture values, you can tell the story in depth through the frame. You can learn more about layers here.

Graphics and geometry. The style that focuses on striking graphics and geometry in urban environments is often called abstract or geometric street photography. It emphasizes visually strong compositions: lines, shapes, patterns, and the interplay of light and shadow in everyday scenes.

Abstract street photography. Purely visual: unusual angles, reflections, shadows, and other techniques that create abstract, sometimes surreal images.

Humor. Capturing funny or ironic moments in everyday life, with a touch of satire: all the head replacements and comic coincidences the street offers.

Color. In color street photography, pay attention to the color relationships within the frame, and how the colors interact with each other.

Still life. While still life isn't typically associated with street photography, you can incorporate its elements by photographing objects and scenes found in the urban environment.

Details. One way to use details is to capture images that suggest a larger narrative: a close-up of a fortune teller's hands, for example. Hands are a very powerful storytelling tool.

These are just a few styles to give you an idea. Street photography is broad, and almost any photographer can find a way to express themselves using the people and elements of the street.
IS STREET PHOTOGRAPHY LEGAL?

The legality of street photography depends on the laws of the specific country or region, so it's highly recommended to check before traveling whether you can photograph there.
In most places, street photography is legal as long as it's conducted in a public space where there's no reasonable expectation of privacy. You can photograph people, buildings, and other elements in public areas such as streets, parks, and sidewalks.
However, restrictions vary by location. Military zones are off-limits, and some places don't allow photographing law enforcement. In India, for example, photography is not allowed in train stations (even though you see plenty of photographs from there, it's forbidden). In some places security concerns make photography difficult; in others you may need a permit.
Street photographers need to know the local laws, and respect the privacy and personal space of the people they photograph. Yes, I know it sounds contradictory, but with time you develop a gut feeling that tells you which situations are okay and which are not.
To simplify: it's usually allowed to take photos on the street. But once you point your camera at someone's house or window, it can be considered an invasion of privacy.
CAN YOU PHOTOGRAPH CHILDREN ON THE STREET?

Legally: check the rules of the place you plan to photograph. Some European laws don't favor street photography much.
Ethically: some people have real issues with a stranger photographing their child, while others are fine with it. As best practice, when parents are around, it's always wise to ask permission. And it matters how you feel: if you feel you're doing something wrong or unethical, just don't do it.
So can you or can't you? It really depends on the location and your attitude. Photographing with a long lens in a park, you're likely to be perceived as a creep. Doing it at a basketball match could be completely fine. You're less likely to meet resistance photographing children in most of Asia, while parents in Europe and the United States have been known to call the police on photographers. There's also the factor of gender: society is more tolerant of female photographers photographing children.
SO, WHAT IS STREET PHOTOGRAPHY?
The best way to describe it: street photography is a captivating art form that lets us document the world around us and tell visual stories through our images. It provides an opportunity to connect with people and places in a more meaningful way, and offers photographers a chance to express their unique perspective and creativity.
If you want to get better at it, start with my guide to developing the photographic eye.

BOOKS ABOUT STREET PHOTOGRAPHY
These are some of the books I'd recommend looking into:
For disclosure: these are Amazon affiliate links, and I might receive a small commission if you decide to purchase one of the books on the list.
- The Americans by Robert Frank - a classic and influential book of black and white photographs taken during Frank's road trip across America in the 1950s.
- Magnum Street Wise by Stephen Maclaren - The definitive collection of street photography from the Magnum agency: iconic images alongside previously unseen work by masters like Cartier-Bresson, Elliott Erwitt, Alex Webb and Martin Parr, organized by the cities and themes that shaped the genre.
- Street Photography Now by Sophie Howarth and Stephen McLaren - a contemporary survey of the best street photographers working today, with interviews and examples of their work.
- Magnum Contact Sheets by Kristen Lubben - a fascinating look at the contact sheets of famous Magnum photographers, including Henri Cartier-Bresson and Elliott Erwitt.
- Humans of New York by Brandon Stanton - a collection of portraits and stories of New Yorkers, which became a hugely popular blog and social media phenomenon.
- The Suffering of Light by Alex Webb - a retrospective of Webb's colorful and complex street photographs taken around the world.
- Bystander: A History of Street Photography by Colin Westerbeck and Joel Meyerowitz - a comprehensive history of the genre, featuring the work of many different photographers.
- Vivian Maier: Street Photographer by John Maloof - the work of the previously unknown street photographer Vivian Maier, discovered after her death.
- Masters of Street Photography by Rob Yarham - a collection of striking images by Melissa Breyer, Giacomo Brunelli, Sally Davies, George Georgiou, Jay Maisel, Jesse Marlow, Rui Palha, Alan Schaller, Alexey Titarenko, Martin U Waltz and others.
- Street Photography: Creative Vision Behind the Lens by Valérie Jardin - a guide to the technical and creative sides of street photography, featuring Jardin's own work.