This document discusses three ways to back up computer files: using a flash drive, online backup, or an external hard drive. It describes the pros and cons of each method. For flash drive backups, the pros are speed and low cost, but flash drives have limited storage lifespan. Online backup allows access from anywhere but may require fees for large storage. External hard drives allow large backups but could be lost or damaged like any physical storage device. The document then provides step-by-step instructions for setting up backups using Dropbox as an example of online backup.