How to ..
What is data? All your photos, emails, documents, movies you might have made, music you have bought, images you have created, novels you have written…all this is your User Data and is kept conveniently in your Home folder, the folder with the picture of a house and your name on it:
It is your responsibility to look after your data — computer warranty only covers the physical parts of the machine, NOT THE DATA. If you have extended warranty (highly recommended) your parts are covered for 3 years and will be replaced free of charge in the event of failure, but not the data!
Backing up means to make a copy of data to a separate hard drive external to the computer. So if the computer hard drive fails — and they do! — you can restore your data onto the new hard drive or import it onto a new computer.
Fortunately since Mac OS 10.5 Leopard automatic backup to an external device is built-in and extremely simple to configure. External hard drives are also very cheap and getting cheaper at about $100. Restoring your data is equally simple.
External Hard drives: there are 2 main types: mains powered and USB powered. The latter are smaller and particularly appropriate for laptops because of their size and lack of extra cables needed by mains hard drives. They are fine for desktops too. Any brand of hard drive will do, they are much of a muchness so buy on price and capacity and they usually start at about 500 gigabytes which is fine for most modern computers unless you are a big movie maker and need much more storage space in which case 1000GB (1terrabyte) will be your staring point. Most modern hard drive connect via a USB cable.
Once you have your hard drive bought you plug it's USB cable into the back of the computer. It won't work properly in the keyboard USB port and its good to have it stashed away at the back: fit and forget!
First the hard drive mounts you should get a message asking: Can Time Machine use "The Name of Your External Hard Drive" it for Backup? Of course you click OK and it will do the rest. If the external drive needs formatting from PC to Mac format Time machine will ask you if it can Erase or Re-format the drive. Once again say OK.
Occasionally it won't ask to backup and the drive will simply mount on the Desktop with an orange icon and just sit there looking hopeful:
When it opens unlock the padlock bottom left with your user password and clcik the Select Disk icon. Another little window will appear with your external hard drives connected: