Crashplan is a backup tool that allows users to back up their data to other computers or their own computer. It has two versions: Crashplan for basic standalone backups between systems, and Crashplan Pro for backing up multiple clients to a server. Crashplan is cross-platform, inexpensive, provides fast and efficient backups with file encryption, and allows backups to any computer. The process involves downloading Crashplan, creating an account, selecting the files and computers to back up, and letting Crashplan run backup jobs continuously or on a schedule.