Generally speaking, there are two types of mammograms. A 2D mammogram makes a two-dimensional image of your breast, while a 3D mammogram uses several images of your breast to create a 3D image.
A 2019 study in women ages 65 and older found that 3D mammograms were more specific and led to a lower false-positive rate than 2D mammograms.
The National Cancer Institute is also doing a large-scale, randomized clinical trial to compare 2D and 3D mammograms in their ability to reduce diagnoses of advanced breast cancer.