The documentary approach is one that many photographers stick to, and it’s essentially taking images as if you are a ‘fly on the wall’ rather than a photographer who takes staged photos.
The documentary style is used to shoot natural photos, rather than those ‘say cheese’ images that you’d have when you were back at school. It’s a popular approach to events and weddings, and in many ways it’s simply visual reporting. Photojournalism is sometimes put into the same category, yet photojournalists will often have strict rules on editing as they do not want to ‘manipulate the truth’.
Every photographer will have their own unique style, but in general the documentary approach is essentially unobtrusive photography, whereby the photographer takes photos from a distance, covering as much of the event as possible.