Focus Focus means how much of the image is sharp, which can be used to emphasis a certain point. For example, if someone stands with their arm out in front of them
Depth of field Depth of field means how much of the image is in focus. You can have a narrow depth of field, where only a small part of the image is in focus, or you can have a larger depth of field, where everything is in focus. Depth of field is controlled by the aperture. A larger aperture means a narrower depth of field.
Aperture The aperture refers to the size of the iris (hole) within the lens. The bigger the hole, the more light gets into the camera.
Shutter speed This is how quickly the shutter opens and closes. The longer the shutter speed, the more light gets into the camera. A short shutter speed will freeze things without much motion, so you can photograph fast moving things like cars or animals.