There are two basic ways to back up computer data:

Removable Backup Tape
The most common method of backup is to record a copy of your data onto some type of removable tape. This can vary from a simple floppy disk to high-tech removable cartridges and tapes. These should be taken off-site each day, so a recent copy of your files can be accessible outside the office in the event of a disaster.

Network Connections
In this case, a firm sends a copy of files to a remote system via a phone line or Internet connection. The information is thus guaranteed to be stored off-site.