Depth of Field

Depth of field is the distance between the nearest and furthest objects that appear in acceptably sharp focus in a photograph.

This picture above shows shallow depth of field. The main object is the football and the background is blurry. This means it's shallow because of the blurry background and the football being the only thing in focus. Shallow depth of field means the background is completely blurry. Which it is here, making it a shallow depth of field. http://learnphotographywithtomgrill.blogspot.com/2011_05_01_archive.html

This picture above shows medium depth of field. The main object are the flowers. This is medium depth of field because the background is still blurry, but you can see the overall shape of it and what it is. So the background isn't too blurry but it's not completely in focus. This is what makes it medium depth of field. https://courtcourt4.wordpress.com/2012/09/20/shallow-medium-and-full-depth-of-field/

This picture above shows great depth of field. The entire picture is in focus. That makes it a great depth of field. The depth of field is great because of everything being in focus, from the foreground to the background. The depth of field in this picture is great so you can see everything in the picture clearly.