Focal length is just what it sounds like. How far away you are from your subject affects how the image presents itself in terms of what is in focus. For this, I took photos of my subject, backing up further and further with each photo and zooming in on my focal length. The focal lengths I used were 18mm, 25mm, 35mm, 50mm, 70mm, 135mm, 200mm, and 300mm. As you can see, the 70mm mark is the most accurate to the subject, and the further or closer I got from the subject, the more warped their features became. For something like portraits, typically 70mm is the best focal length, but for this and other photos, focal length can be used to further manipulate the photo to how you want it to be viewed.