Mammograms are used for both screening and diagnosis.
A screening mammogram is used to find breast changes in women who have no signs of breast cancer. Most women get two x-rays of each breast.
If your screening mammogram shows a breast change since your last one, or if you or your health care provider notices a change, you may need to have a diagnostic mammogram. That means more x-rays are taken to get clearer, more detailed pictures of the breast.
A digital mammogram is another way to take a picture of your breasts. The procedure for having a digital mammogram is the same as for a screening mammogram, except that it records the x-ray images in computer code instead of on x-ray film.
This answer is based on source information from the National Cancer Institute.