Time Machine is a backup app that works with your Mac and an external drive or AirPort Time Capsule (Sold Separately). Time Capsule might be the first choice for laptop users since using it will make you able to backup over Wi-Fi which is great.
Connect the drive, let the Time Machine use it, and that’s it! Time Machine automatically backs up your entire Mac, including system files, apps, accounts, email messages, music, photos, videos, and notes. But Time Machine is more different than any other backup app and that is because it doesn’t not only keep a copy of every file you have, it also remembers how your device looked on any day you want.
Simply you can see your Mac as it appeared in the last week for example. Time Machine automatically keeps hourly backups for the past 24 hours, daily backups for the past month, and weekly backups until your backup drive is full. You don’t need to worry about the important information on your hard disk anymore.
To determine the size of the backup drive needed, you can buy one that is 1.5 to 2 larger that your current hard disk in your Mac. So if you have a Mac with a 500GB drive get at least a 1TB external drive.
Apple made setting up Time Machine as easy as possible. If you have a secondary internal hard drive in your Mac you can use that as your backup drive.