The aim of a photojournalist is essentially to capture reality, and as such they need to be in the right place at the right time to capture a moment or significant event that is newsworthy. As a genre, documentary photography, captures reality, but it also has the advantage to tell a story over a longer period of time with the aim of raising awareness of a particular subject.
Photojournalists and documentary photographers may capture the facts, but they also interpret what they see. This could be achieved by cropping or emphasising their subjects to suggest a certain emotion or angle of the storyline. Unless present at the time of the event, the audience of the image may rely only on the visual information which the photographer has chosen to focus.