The length of time that the camera is exposed to light. You would want a long shutter speed if it is dark and a short one if it is light out. The longer the shutter speed is the more blur there is in the picture if there was movement. If you are photographing sports or anything moving you want a fast shutter speed so there isn't blur.
Aperture is the depth of field. You can have either a shallow or wide depth of field. The larger the number is the smaller the hole is which is used for landscape pictures. The larger numbers of aperture start small and get larger like a megaphone which is why it is used for landscapes. The smaller numbers of aperture start big and get small.
ISO is how sensitive the camera is to light. If there isn't a lot of light you want to use a high ISO so the camera is more sensitive to light. If it is a sunny day you want to use a low ISO because there is already natural light.
White balance is removing unrealistic colors from a photo.