Base backup -- A complete backup of the data or system
Differential Backup -- A backup of all data currently on the disk that has changed since the last full backup. Each day's differential backup tends to be a bit larger than the previous one.
Incremental Backup -- A backup of all files changed since the previous backup, either base or incremental.
Backup to tape -- A backup which uses tape as the destination (in this case, in our 87-tape autoloading library)
Backup to disk -- A backup which uses disk space as the destination (either presenting itself as a disk volume or emulating a tape drive). We are currently using a fibre-channel based disk array to provide enough space to do backup to disk for some systems.
System snapshots -- A backup of a VMware-hosted virtual server which allows us to take a disk-based backup similar to an image backup while the virtual server is running. This serves two purposes. One, we can make a snapshot before a planned upgrade, and easily roll back the entire virtual server if something goes wrong, and two, it serves as a disaster recovery tool. A system can be restored to a recent state, even to a different disk in a different location, and brought up. If needed, additional restores of files or databases backed up through other methods could then be performed.
Image backup -- A backup of physical disk blocks. We currently do not have the ability to do image backups. The advantage of image backups are speed and much smaller incremental backup space requirements.