When we look through the viewfinder or at the LCD screen, the image is normally presented in a Landscape (horizontal) format and with a 3:2 ratio, inherited from the old film negatives which measured 36mm wide by 24mm high (which gives the ratio of 3:2).  This 3:2 ratio doesn't have to be used, as the technique of cropping allows us to change that ratio to one more suited to the particular image.  In the examples below you can see the original 3:2 ratio, which I have changed to a square 1:1 ratio.  Thanks to Gillian, Liz, Louise and Dominic for the use of their images to demonstrate the way cropping an image can change how it looks.  Similarly the use of letterbox or panoramic cropping can change the way an image looks.