Liver spots and sun spots, medically known as lentigos and seborrheic keratoses are benign growths that are very common.
They can happen in sun exposed areas or non-sun exposed areas, like the back and abdomen. They do not turn into skin cancer. They can be flat or elevated. They can be brown or black or multiple-colored, but often times they look stuck-on or sticker-like and seem out of place. The best way to determine whether one of these spots is dangerous or not is to compare them to the other spots you have.
If you notice something that looks out of place, that's when you need to see a dermatologist to get a skin biopsy.