A mammogram is a screening test for breast cancer which uses special X-ray images to detect abnormal growths or changes in breast tissue.
Using a digital X-ray machine made especially for breast tissue, a technologist compresses the breast and takes pictures from at least two different angles, creating a set of images for each of your breasts. This set of images is called a mammogram. Breast tissue appears white and opaque and fatty tissue appears darker and translucent. Many centers also do 3-D mammography. This is similar to regular mammograms but many more pictures of the breast are taken at various angles to produce a 3-D picture for the radiologist to check.
The mammogram is used to look for lumps or other findings that are too small to be felt during a physical exam. A mammogram can also help your doctor determine the next step if a lump, growth, or change in your breast is found.
Why Do I Need a Mammogram?
The risk of breast cancer increases with age. That is why it is very important for all menopausal women to get regular mammograms.
Mammography is your best defense against breast cancer because it can detect the disease in its early stages, before it can be felt during a breast exam. Research has shown that mammography can increase breast cancer survival.
Source credit https://www.webmd.com/menopause/guide/guide-mammogram-testing#1