In June of last year, Google introduced phone prompts that made using two-step verification easier than ever. These proved popular, being more secure and simple to use than SMS codes. In February of this year, Google updated these prompts to show more information about the device attempting to sign into your account. And soon, the company will begin pushing these prompts to users of the older, less seamless SMS two-step verification method.
Beginning next week, two-step SMS users will be shown a preview of the newer prompts when they sign in, at which point they can choose to keep it enabled or continue to use SMS. Google says the reasoning behind this move is because of security reasons; text messages and one-time codes are apparently more vulnerable to phishing attempts. Using the prompts will ensure that authentication is going through an encrypted connection.
So if you're still using the SMS codes, keep an eye out for an invitation to use the prompts. Give them a shot if you haven't already; as long as you have an Internet connection on your phone, there are virtually no disadvantages.