Two-factor authentication (2FA) requires a user of a software application to present two types of evidence to prove they are who they claim to be. In practice, a user will often present a password and a short code sent to their mobile device via Short Message Service (SMS).
While this is generally considered more secure than using a single factor (such as a password alone) for authentication, it is considered slightly less secure than using two-factor authentication with a password and a physical security key (among other potential alternate second factors). This is because messages sent via SMS can be vulnerable to attacks like SIM swapping, potential interception via an international mobile subscriber identity (IMSI) catcher, or can fall into the wrong hands via other methods.
As mentioned above, it is still generally considered more secure to use two-factor authentication with the second factor delivered via SMS than it is to use a single factor alone. However, if you have the option to switch to a physical security key as your second factor, you should consider that instead of having a code delivered via SMS.