Full images - Backs up everything on the selected disks/partitions, not requiring an previous backup. They are going to be the largest file and take the longest to create. But they are the safest.
Differential Images - A backup image of the selected disks/partitions that contains only data changed from a previous full image. It requires a full image for reference. These file are smaller than fill images but not as small as incrementals, and take less time to create than full images.
Incremental Images - An image of selected disks/partitions that contains only data changed from a previous incremental image. These backup images require previous incremental images, functioning as a link in a chain. If one link is bad/damaged the chain is useless. This image type is going to be the smallest and fastest to create but they are also the most risky, given their reliance on previous incremental images.
Read more about the subject here.
Differential Images - A backup image of the selected disks/partitions that contains only data changed from a previous full image. It requires a full image for reference. These file are smaller than fill images but not as small as incrementals, and take less time to create than full images.
Incremental Images - An image of selected disks/partitions that contains only data changed from a previous incremental image. These backup images require previous incremental images, functioning as a link in a chain. If one link is bad/damaged the chain is useless. This image type is going to be the smallest and fastest to create but they are also the most risky, given their reliance on previous incremental images.
Read more about the subject here.