There are several types of backups available and sometimes a combination of backups is required for a full recovery. It is important to understand which backups are necessary in order to properly store your data.
Typically, a full backup captures the entire system including the operating system and any settings that are configured. This backup takes a great deal of time because it encompasses all of the data available. It is important that you keep a recent full backup accessible incase a recovery is required.
This backup focuses solely on the data that has recently changed between the current state and the last full backup. When files are lost, or a recovery is required, the combination of the full backup and the differential backup are required.
An incremental backup takes less space than a differential backup because it captures change in data from its current state and last backup, even if the last backup was not a full backup. A recovery requires the last full backup as well as all of the incremental backups.