It can change a lot of things like what you are trying to convey or even emotion.
Explanation:
When you take a picture you are telling a story about something. And what part of the contents you take a picture of can change your effect of a photo.
For example a speech
If you focus your picture on the speaker can change the effect if you are focusing on the crowd. You could take a photo of the crowd to rely the emotion of the speaker, etc. the list goes on.
You have to have a set goal of what you want to tell the viewer.
