Two-step verification is a security process that requires the user to have a password and a physical device such as a smart phone, card or USB device. For example if you are going to log into the website that had a two-step verification you would have to know the password and retrieve a passcode from your phone in order to access the website. If someone steals your password they would not be able to access the website unless they have your phone as well. This makes it much more difficult for someone to hack into your accounts.
Two-step verification is a process involving two subsequent but dependent stages to check the identity of an entity trying to access services in a computer or in a network with just one factor or secret, whilst there is no proof obtained that the bearer of the unit is identical to the owner of the unit.
This is the simplest case of a multi-factor authentication, which might involve only one of the three types of authentication factors (a knowledge factor, a possession factor, and an inherence factor) for both steps.
In just technical procedures with portable units, all information contained in the unit does not provide authentical evidence about the identity of bearer and owner. Only when each step of an authentication procedure involves a set of two different and independent authentication factors provided by the bearer then the preliminary technical verification gets extended via real authentication finally to two-factor authentication TFA.
In common one (single) factor authentication procedures, the name of the owner and her/his personal secret are formally not independent, as they get used generally in invariant coherence. This has to be taken into account especially when the personal name of the owner of the personal secret is openly displayed.
We will see an increase of websites that offer two-step verification in order to access information. I would recommend using that option if it becomes available as it will make it substantially harder for a hacker/thief to access your online accounts.
Here’s the link to Google’s two-step verification process.
Here’s a link to Apple’s two-step verification process.