Depth of field is a photography thing. Imagine taking a picture of your toys on the floor. When you take the picture, only some of your toys might be really clear and in focus, while others might be blurry or fuzzy. This is because the camera can only focus on certain things at a time. The area of the picture that is in focus is called the depth of field.
When the depth of field is shallow, only a few things in the picture will be in focus. This can make your subject stand out really well, but it also means that everything behind or in front of your subject might be blurry or fuzzy.
When the depth of field is deep, more things in the picture will be in focus. This can be good for landscape pictures or when you want to show a whole scene.
Some cameras have settings that let you control the depth of field, so you can make sure your picture looks just how you want it to.