Depth of field refers to the distance between the nearest and farthest objects that appear sharp in a photo. There are two types: minimum depth of field, where only one section is in focus, and maximum depth of field, where everything appears sharp. The document discusses photos that demonstrate each type and expresses a preference for minimum depth of field, citing a photo of a cat's nose in focus as inspiration for accentuating features in a makeup project. It also acknowledges that maximum depth of field could be useful for portrait-based shoots where the entire face needs to be in focus.