Apple’s two-step authentication process is designed to make your Apple ID more secure. When attempting to reset a password or make other kinds of account changes, a separate verification code is sent to an iOS device you own. That code is then used to verify that you are who you claim to be before you’re allowed to make any changes.
Many big tech companies have offered two-step authentication for quite some time, and Apple’s process is only a couple months old.
Now that security researchers have had time to dig through Apple’s implementation of two-step, some problems have surfaced. Once the login details for an Apple ID with two-step authentication enabled are compromised, there’s nothing stopping hackers from accessing iCloud data, like device backups.