Time Machine to a disk connected to your network
Alternatively, you can use Time Machine to back up to a disk that is connected directly to your network rather than to a specific Mac. This means it’s available to all the computers on your network so you can have them backing up centrally, and best of all, they back up completely automatically over the network every hour (either via Wi-Fi or ethernet, depending on how they connect to it). This is great for laptops especially: now you don’t have to remember to connect your backup disk; it just does it automatically whenever the Mac is awake.
Most people will think of Apple’s Time Capsule for this method—a network router with a built-in hard disk—and indeed it’s the simplest option, but you don’t have to go with that. Plugging a hard disk into an AirPort Extreme’s USB port will make it available on the network for Time Machine, and lots of other Network-Attached Storage (NAS) devices from companies other than Apple also support Time Machine backup. Indeed, they can offer other features besides; see “Fire- and waterproof disks,” below.
Good because: All the advantages of Time Machine, but more convenient, especially for laptop users, since backups happen automatically over your home network.
But be aware that: Backups are a little slower (or indeed can be much slower, depending on the speed of your network or the bandwidth of the method by which your Macs connect to it) and restoring is even slower still. You have to be connected to your home network. A little extra complexity. And no protection against theft or other local disasters.