In this lesson on backing up your Mac, I look at why you want to use Time Machine to back up your Mac instead of iCloud. In short form, Time Machine backs up everyting on your Mac by default. This includes photos, movies, files, applications, and even external hard drives. iCloud just keeps a small number of folders in sync, as well as your notes, reminders, calendar, and other items. It does not back up your entire hard drive or Mac and is not considered a backup for the Mac.