Originally Posted by Proplus:
Mac Basics: Time Machine backs up your Mac - Apple Support
Its basically a function built into OSX. Just plug in an external HDD and switch Time Machine on, it'll auto back up every hour (subsequent backups after the first one only backs up changes made so does not keep taking up lots of storage space), and keeps older backups like once a week and once a month. Its backs up literally your whole Mac, including the apps, so if you ever want to do a wipe of your Mac or get a new one, just restore from a backup and voila. Stuff like Microsoft Office will get restored, without the need to enter the Activation Key again.
One other feature is you can enter Time Machine at any time. You can glimpse back to any of the backups in Time Machine and select the specific file or folder you want from then and retrieve it, comes in handy when you've accidentally lost a file or did some unwanted editing and saved the file by mistake.
If you don't want to have a wire (USB or Thunderbolt) connected to your Mac to do Time Machine backups, then you have 2 choices:
1. Get a Time Capsule, put simply this is rather like a Airport Extreme with a HDD built in, so you can wirelessly do Time Machine backups to it. The older Airport Extremes allowed you to plug in a USB HDD to it and could do the same, but not anymore with the latest model.
2. Get a network drive that will support Time Machine. I recently purchased a WD 3Tb MyCloud and it natively supports Time Machine backing up, so I've hooked it up via LAN to my router. I got this for "friend's" price for HK$700, and it normally retails for around HK$1100-1200, but still is a good cheap option.