Once this setting is activated (oh, why can’t Facebook just do it on our behalf just like how they sneakily reset our privacy settings in the past with a new rollout?), Facebook will send a text message to your handset alongside an access code which you are required to input before the signing on process is completed.
Once done, whenever your account is accessed from a device that was previously unassociated with your account, Facebook will send a confirmation code to your phone, instructing you to complete the login.
Of course, if you happen to lose your phone while the login approvals setting are left on, you will need to go to the nearest computer, log into Facebook and amend the settings from there. Do you think this will suffice at the moment as an added security measure, or must more be done?