Two Factor Authentication, also known as 2FA, two step verification or TFA (as an acronym), is an extra layer of security that is known as "multi factor authentication" that requires not only a password and username but also something that only, and only, that user has on them, i.e. a piece of information only they should know or have immediately to hand - such as a mobile phone. Using a username and password together with a piece of information that only the user knows makes it harder for potential intruders to gain access and steal that person's personal data or identity.
Swyftx supports any apps that use time based 2FA generators such as Authy (backs up to the cloud), Google Authenticator Android or iOS (very popular) or SMS. Codes generated from these apps on a registered mobile device will be required to login and withdraw funds from your account.
Always backup the recovery code provided to you during the setup phase. Without these you won't be able to get back into your account if you lose access to your mobile device.